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F1000Research

2046-1402

F1000 Research Limited

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10.12688/f1000research.110911.3

Research Article

Articles

Alteration in central vascular and cognitive functions during simulated work conditions in males – a secondary analysis from a randomised controlled trial

[version 3; peer review: 1 approved, 2 not approved]

Shruthi Paramshiva

Poovitha

Investigation Methodology https://orcid.org/0000-0002-6267-7266 1 Chandran M

Obhuli

Conceptualization https://orcid.org/0000-0001-5515-6377 2 Chandrasekaran

Baskaran

Data Curation Writing – Original Draft Preparation https://orcid.org/0000-0003-1439-9158 3 K.

Vaishali

Conceptualization Methodology https://orcid.org/0000-0001-5746-1682 4 Sukumar

Suresh

Investigation Writing – Review & Editing https://orcid.org/0000-0001-9345-9790 2 Kadavigere

Rajagopal

Supervision https://orcid.org/0000-0003-3486-8740 a 5 1Division of Yoga, Center for Integrative Medicine and Research Manipal Academy of Higher Education, Manipal, karnataka, 576104, India 2Department of Medical Imaging Technology, Manipal College of Health Professions Manipal Academy of Higher Education, manipal, karnataka, 576104, India 3Department of Exercise and Sports Sciences, Manipal College of Health Professions Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India 4Department of Physiotherapy, Manipal College of Health Professions Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India 5Department Radio diagnosis and Imaging, Kasturba Medical College Manipal Academy of Higher Education, Manipal, Karnataka, 576104, India

a rajagopal.kv@manipal.edu

No competing interests were disclosed.

29 1 2025

2022

397

22 1 2025

2025

This is an open access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Background

Methods

We administered a randomised controlled trial investigating the effects of various intensities' micro-breaks on central vascular and cognitive functions during simulated work conditions for four hours. The carotid artery hemodynamics and cognitive functions were measured by Duplex ultrasound at 0 ^th, 2 ^nd and 4 ^th hour and computer-based Flanker tests at 0 ^th, 1 ^st, 2 ^nd, 3 ^rd and 4 ^th hour of visit days, respectively. From the randomised controlled trial, we extracted the secondary data of carotid artery hemodynamics and cognitive functions change at the 4 ^th hour from the baseline and analysed for any relation.

Results

Though we observed linear relation between the carotid artery hemodynamics and the executive functions, the relation was not statistically significant. we found a significant reduction in carotid artery diameter during prolonged sitting (0.03 cm [95%CI 0.01, 0.05]), velocity (10.35 cm/s [95%CI -2.85, 17.86]) and shear rate during interrupted sitting (174.39 [95%CI 65.67, 283.11]) We found increased accuracy during prolonged sitting (12.7% [95%CI 0.66, 24.81]) and sitting with light-intensity activity breaks (6.92% [95%CI 1.39, 12.44]). We did not find any significant relation between the change in central vascular functions (carotid artery diameter, velocity, shear rate and blood flow) and the cognitive functions during three different work conditions.

Conclusion

Though a significant relation between carotid artery function and cognitive function could not be established, microbreaks can mitigate the vascular and cognitive risks associated with prolonged sitting.

Prolonged sitting Central vascular function Blood flow Velocity Doppler Micro-breaks Cognition

Manipal Academy of Higher Education

Baskaran Chandrasekaran received a faculty seed grant from Manipal Academy of Higher Education for the present research.

The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Revised Amendments from Version 2

The additional references are added as suggested by the reviewer.

1. Introduction

Profound dynamic changes in the endothelial functions in early adulthood is associated with early atherosclerosis and cardiovascular disease risk in late adulthood. ¹ ^– ³ High sedentary behavior (sitting activities with low energy expenditure less than 1.5 metabolic equivalents) is now identified to be the independent risk factor for the early atherogenesis and cardio-metabolic disease risk. ⁴ ^, ⁵ However, high sedentary behavior is evident and continue to rise globally and in contextual settings such as workplace and schools. ⁶ ^– ⁸ Hence it is imperative to address contextual sedentary behavior through administering movement based micro-breaks. ⁹ ^, ¹⁰ Empirical evidence elucidating the efficacy of advocating activity breaks during the prolonged sitting time on cardiometabolic disease risk and cognitive decline remains mixed. ¹¹ ^– ¹³

Mechanistic plausible mechanisms have linked central vascular functions and resulting cortical perfusion to cognitive functions such as memory, attention, visuospatial skills and cognitive control. ¹⁰ ^, ¹⁴ ^, ¹⁵ Executive functions and working memory influences common work-related skills: decision making and problem-solving, resulting in better work productivity. ¹⁶ ^, ¹⁷ The alteration in the vascular function and the resulting cognitive functions are viewed as plausible mechanistic links to poor problem-solving skills and low work productivity. ¹⁸ ^– ²⁰ Few epidemiological evidence and acute laboratory studies have attempted to elucidate the above possible association between vascular endothelial functions, cognitive functions, and work productivity however, it remains inconclusive. ²¹ ^– ²³

We attempted to explore the possible association between the central vascular functions and the executive functions in simulated sedentary and active work conditions. We hypothesised that the subtle association between central vascular functions and executive functions may foster occupational health experts to design appropriate public health and behavioral strategies to culminate the adverse effects of work conditions on central vascular and cognitive functions, which may improve work productivity.

2. Methods

The present findings are the results of the secondary analysis of our ongoing randomised controlled trial. Kasturba Hospitals Institutional Ethics Committee (IEC 383-2021) approved the study and was prospectively registered in India's Clinical Registry (CTRI/2021/09/036496). The study was conducted and conforms to the research principles of the Declaration of Helsinki. ²⁴

2.1 Study design

The findings of the study are derived from a randomized crossover trial that investigates the effects of passive and active work conditions on central vascular functions and cognitive control in young adults.

The study was conducted in the ultrasound testing room, department of radiodiagnosis and imaging of a multidisciplinary teaching hospital. The study was conducted between September 2021 – December 2021. Potential participants were randomised to one sedentary and two active work conditions for four hours, with each study visit was separated by a wash-out period of at least six days. The whole study design is depicted in Figure 1. The present study explored the relation between the dynamic carotid vascular changes (diameter, velocity, shear rate and blood flow) and executive functions. We explored the possible association of cognitive functions and the dynamic carotid artery functions with the lifestyle factors such as physical activity, smoking, alcoholism and body composition.

Figure 1. Design of the present study.

The participants were randomised to the three different behavioral interventions in simulated work conditions for four hours: (1) SIT (uninterrupted sitting for four hours with bathroom breaks only); (2) LIT (sitting interrupted with light intensity walking breaks for three minutes every one hour for four hours of the study period; MIT (sitting interrupted moderate-intensity stair climbing breaks for three minutes every one hour for four hours of the study period). Doppler ultrasound-mediated carotid, superficial femoral artery diameter and velocity were measured every two hours of each visit period, and computer-based executive functions were measured every hour of each visit period.

2.2 Participants

Young adults of age 25 – 35 years of both genders belonging to a single university were invited to the study through the official Exchange student emails, brochures in college and hostel noticeboards. Due to cultural barriers for Doppler ultrasound measurement, only male students volunteered for the study. To be eligible, the potential participants should be physically inactive (self-reported physical activity levels of less than 600 METmin/week International Physical Activity Questionnaire IPAQ), optimum levels of visual acuity (> 5/6) for operating the computer-based cognitive tests with adequate lower limb strength to walk or climb stairs for three minutes. Participants with self-reported cardiometabolic diseases, recent musculoskeletal trauma < three weeks or self-reported depressive disorders affecting physical activity or cognitive measurement were excluded from the study. Further, the volunteers willing to dedicate at least six weekday hours were included in the study.

2.3 Measures

2.3.1 Vascular functions

The vascular functions using Doppler ultrasound was measured as stated and administered in the earlier studies. ⁹ ^, ²⁵ ^– ³⁰ Dynamic central (right carotid artery) and peripheral vascular (Superficial Femoral Artery) functions [diameter, velocity] were measured using Duplex ultrasound (GE Voluson Swift, Germany) at a pulsed frequency of 50 MHz using the probe insonated at an angle of 60° were used. The diameter and the velocity were automatically measured using inbuilt edge-detection software, and the captured images were analysed using B Mode images and confirmed with the carotid artery’s diameter and velocity. Shear rate was calculated using the formula: 4 × [mean blood velocity/arterial diameter]. The maximal blood flow was calculated from continuous diameter and mean blood velocity recordings using the following equation: 3.14*(diameter/2) ² * mean blood velocity *60. ³¹

2.3.2 Executive functions

Executive functions or cognitive control was assessed using the computer-based Response Inhibition test, Eriksen Flanker paradigm (Milliseconds, Inquist). The participants were presented with the visual stimuli on a laptop using Inquist 6.0 software (Millisecond Software, Seattle, WA, USA).

The participants were shown a line with five alphabets H, K, S &C with the central alphabet as the target and flankers on the sides. The participants were instructed to focus on the central alphabet and press either Q or P based on the H or K, and S or C displayed on the left and right sides of the computer screen, respectively. The task had two types of trials: congruent (noise) and incongruent (no noise) trials. All the alphabets are the same in congruent trials, while the flanker and target alphabets were different in the incongruent trials. A total of 120 trials (60 congruent, 60 incongruent) were presented to the participants, which were randomly sampled. Each trial lasted for 3000 ms, with an interstimulus interval of 1500 ms. The participants were given a one min break after every 40 trials. The data were automatically stored in the inquisit software and retrieved as csv files later for analysis.

2.4 ‘Snack’ivity interventions

We administered activity interruptions during sitting at two different intensities: (1) Light Intensity Task (LIT): The participants were asked to walk in the 30-meter laboratory hallway at their comfortable pace (perceived exertion less than 11 in original Borg’s scale) for three minutes every hour during this intervention visit; (2) Moderate Intensity Task (MIT): The participants were asked to climb laboratory stairs of 20 cm with a self-selected stepping rate (perceived exertion of 13-15 corresponding to in original Borg’s scale) for three minutes every hour during this intervention visit.

2.5 Procedure

In the present study, the participants had visited the laboratory four times, of which one was a familiarisation session, and the other three were interventional visits. On the first study visit, the participants were familiarised with the standardised procedures of vascular and executive functions measurement along with the familiarisation of hallway walk (LIT) and stair climbing (MIT). Further, the intervention order (SIT, LIT and MIT) was randomised using computer randomisation ( www.randomiser.org). The participants were asked to pick the concealed envelopes of the random generated treatment orders, and the order was followed for the subsequent visits. On the second visit, the patient arrived between 8:00 AM-9:00 AM to reduce the effect of the diurnal variation on the vascular and cognitive function. The patients were instructed to refrain from smoking, alcohol and any vigorous activity for at least 48 hours prior to the second, third and fourth study visits. The potential participants were given an asleep food diary log and ensured adequate sleep for at least 8 hours, and the previous dinner was at least separated by 12 hours from the study visit. The participants were transported from their location to the lab by means of the motor vehicle to avoid any vigorous activity during the travel. After baseline vascular and cognitive measures, the participants were given a standard breakfast (idly with dhal kichadi on participants preference) which ensured 33% of the daily calorie consumption based on the food log during the familiarisation visit. The study visits, including measurement and interventions, took place in the temperature and humidity-controlled laboratory (26°C and 84% humidity).

Based on the order of the randomisation, the participants underwent SIT or LIT or MIT interventions. During the SIT intervention visit, the participants were instructed to perform their day work (read, write or watch non-stimulant videos of their preference) for the next four hours (9:00 – 1:00 PM) in the uninterrupted sitting position with minimal lower limb movements. If the participant wished to use the bathroom in the middle of the study visit, the participants were passively transferred to the western toilet using a wheelchair. A researcher monitored and ensured to avoid the unpurposeful movements in the participants during all three study visits. The participants followed a similar work simulation during LIT intervention, except they interrupted their sitting time by self-paced walking for three minutes every hour in the laboratory hallway. During the MIT intervention visit day, the participants interrupted their sitting time by three minutes of stair climbing every one hour at a self-selected stair climbing velocity. The participants were instructed to select a climbing velocity that may induce a moderate-intensity effort (exertion level of 13 and above).

The central (right common carotid artery) and peripheral (right superficial femoral artery) vascular functions were measured at baseline, 2 ^nd hour, and 4 ^th hour, whereas the computer-based executive functions were measured every one hour (0 ^th, 1 ^st, 2 ^nd, 3 ^rd, 4 ^th hour).

2.6 Data analysis

The present study results are part of secondary analysis from a randomised controlled trial. We have presented the baseline demographics, cerebral vascular and cognitive functions as mean and standard deviation after log-transformed the non-normal data. The normalisation was assessed using the Shapiro Wilk test, and in the case of non-normality, the variables were log-transformed. The change in the central vascular and executive functions before and after 4 hours of the three study visits was calculated using excel 2016. The mean change in the central vascular and executive functions at the 4 ^th hour from the baseline using paired t-tests and effect size using Cohen d. The relation between the mean change in the central vascular functions (diameter, velocity and shear rate) and the executive functions (reaction times and accuracy) before and after four hours were analysed using the Pearson correlation and multiple linear regression model with the executive function as the dependant variables and the covariates as central vascular function controlling for baseline demographic variables. All the statistical treatments were analysed using statistical software JASP version 0.14.0 (University of Amsterdam, Netherlands).

2.6.1 Power calculation

As the presented data is a secondary analysis of a randomised controlled trial, the presented sample size was also calculated for the randomised controlled trial. For the randomised controlled trial, we have estimated our sample size as 14 participants to have at least a difference in blood flow velocity of 0.45 ml/min with the moderate effect (Cohen d = 0.45) between the SIT and LIT interventions at 95% level of significance and 80% power. With an assumed drop of 20% of the sample for the three study visits, we have included 17 participants. The sample size was calculated using a software program (G*Power version 3.1.9.6, Universitat Kiel, Germany). ³²

3. Results

Seventeen males volunteered for the study, and all of them completed all three study visits that were six-seven days apart. Only male participants participated in the study as the females were reluctant for the lower limb vascular function study. Of 22 participants volunteered for the study, 17 participants were found to be eligible due to potential reasons displayed in Figure 2. All the 17 participants completed the 4 day experimental visits with no missing data. Figure 2 shows the inclusion of the participants and the secondary data extracted from the cross over trial.

Figure 2. Flowchart showing the screening, inclusion of the participants and the secondary analysis of the data extracted from the randomised cross over trial. 3.1 Baseline characteristics

The majority of the participants (n = 16; 94%) had a normal BMI, whereas one volunteer was found to be obese with a mean BMI of 24.88 ± 3.50. Many of the participants (n = 10; 55.85%) were found to have at least one lifestyle risk factor, such as smoking or alcohol. The majority of the participants (n = 14; 82.35%) were found to be physically inactive. We did not find any significant differences among the carotid artery variables or executive function variables during all the active and passive work conditions from baseline except the reaction times. Table 1 demonstrates the baseline characteristics (demographic, central vascular and executive functions) of the included study participants.

Table 1. Baseline characteristics of the participants.

Variables		Mean ± SD	n (%)	Significance (p *)
Age		24.41 ± 3.84
Body Mass Index		24.88 ± 3.50
Waist circumference (cm)		97.32 ± 6.31
Education	Undergraduate		5 (29.41)
Education	Postgraduate		12 (70.58)
Experience (> one year)			11 (64.71)
Smoking (yes)			8 (47.06)
Alcohol (yes)			11 (64.71)
Endothelial functions
Carotid artery diameter (cm)	SIT	0.638 ± 0.075		0.176
	LIT	0.650 ± 0.080
	MIT	0.604 ± 0.064
Carotid artery velocity (cm/s)	SIT	120.76 ± 16.97		0.380
	LIT	118.07 ± 12.51
	MIT	125.00 ± 13.66
Carotid artery shear stress	SIT	1541.65 ± 348.05		0.170
	LIT	1479.46 ± 281.54
	MIT	1682.17 ± 314.62
Carotid artery blood flow	SIT	2327.68 ± 582.49		0.461
	LIT	2371.96 ± 626.86
	MIT	2148.70 ± 416.37
Executive functions
Reaction times (ms)	SIT	474.45 ± 115.80		<0.001 **
	LIT	547.56 ± 68.33
	MIT	601.61 ± 75.93
Accuracy (%)	SIT	77.18 ± 15.94		0.101
	LIT	85.51 ± 6.61
	MIT	78.86 ± 10.88

Abbreviations: SIT = uninterrupted sitting; LIT = Sitting interrupted with light-intensity activity; MIT = sitting interrupted with moderate-intensity activity.

Differences among SIT, LIT, MIT variables are assessed using analysis of variance.

p = 0.001.

3.2 Change in central vascular endothelial functions and the executive functions within the conditions:

When the central vascular functions and cognitive functions change were compared at the fourth hour with the baseline, we found a significant reduction in carotid artery diameter during SIT (0.03 cm [95%CI 0.01, 0.05], Cohen’s d = 0.677), velocity (10.35 cm/s [95%CI -2.85, 17.86], Cohen’s d = 0.709) and shear rate during MIT (174.39 [95%CI 65.67, 283.11], Cohen’s d = 0.825), reaction times during MIT (54.10 ms [95%CI 15.06, 93.22], Cohen’s d = 0.8712), accuracy during SIT (12.7% [95%CI 0.66, 24.81], Cohen’s d = 0.542) and LIT (6.92% [95%CI 1.39, 12.44], Cohen’s d = 0.644). However we found a significant increase in carotid artery shear stress during SIT (-129.30 [95%CI -255.61, -2.98], Cohen’s d = -0.526 and accuracy during MIT conditions (-3% [95%CI -7.38, 2.03], Cohen’s d = -0.292). We did not find significant variation in other central vascular and executive function variables among three different working conditions. Table 2 illustrates the mean change of the cognitive and central vascular functions at the fourth hour from the baseline among the three different working conditions of SIT, LIT and MIT.

Table 2. Change in central vascular endothelial functions and the executive functions within the conditions.

Variables	Interventions
	SIT			LIT			MIT
	T ₀	T ₄	T ₀ - T ₄ ^¶	T ₀	T ₄	T ₀ - T ₄ ^¶	T ₀	T ₄	T ₀ - T ₄ ^¶
Central vascular functions
Carotid artery diameter (cm)	0.64±0.08	0.61±0.07	0.03±0.01 **	0.65±0.08	0.63±0.08	0.02±0.01	0.60±0.06	0.62±0.07	-0.01±0.01
Carotid artery velocity (cm/s)	120.76±16.97	125.92±18.71	-5.17±3.85	118.07±12.51	123.18±15.06	-5.11±3.24	125±13.66	114.65±19.09	10.35±3.54 **
Carotid artery shear rate (/s)	1541.65±348.05	1670.94±332.68	-129.30±59.58 *	1479.46±281.54	1588.62±275.31	-109.16±69.42	1682.17±314.62	1507.78±352.15	174.39±51.29 **
Carotid artery blood flow	2337.68±582.49	2239.51±651.90	88.17±99.51	2371.96±626.86	2325.88 ±644.57	46.08±63.47	2148.70.±416.37	2086.40 ±609.60	62.31±122.49
Executive functions
Reaction times (ms)	474.45±115.80	377.03±255.84	97.42±60.30	547.56±68.33	519.582±99.92	27.98±23.76	601.61±75.93	547.47±74.60	54.14±18.44 **
Accuracy (%)	77.18±15.94	64.44 ±17.79	12.74±5.70 *	85.51±6.16	78.59±13.89	6.92±2.61 *	78.86±10.88	81.54±10.21	-2.67±2.22

Abbreviations: SIT = uninterrupted sitting, LIT = Sitting interrupted by light intensity activity, MIT = sitting interrupted by moderate intensity activity, T0 = measurement value at baseline, T4 = measurement value at the baseline, T0-T4 = mean change in the values compared to baseline and forth hour.

^¶

= values calculated from the paired t test,

= p < 0.05,

= p < 0.01, * &** - denotes level of significance.

3.3 Correlation among changes in central vascular functions and the cognitive functions

We did not find any significant relation between the change in central vascular functions (carotid artery diameter, velocity, shear rate and blood flow) and the cognitive functions during three different work conditions. Table 3 revealed no significant correlation among the central vascular and cognitive functions change between the 0 ^th hour and 4 ^th hour during different work postures. Multiple linear regression also revealed no significant association between the change central vascular and cognitive functions within the conditions ( Figure 3A, 3B and 3C)

Table 3. Correlation among changes in central vascular functions and the cognitive functions.

Central vascular functions		Executive functions
		Reaction times (ms)			Accuracy (%)
		SIT	LIT	MIT	SIT	LIT	MIT
Diameter (cm)	SIT	0.101 (0.699)			0.015 (0.953)
	LIT		0.162 (0.534)			0.062 (0.812)
	MIT			0.069 (0.793)			-0.102 (0.704)
Velocity (cm/s)	SIT	-0.265 (0.303)			-0.350 (0.169)
	LIT		-0.051 (0.847			0.095 (0.718)
	MIT			0.038 (0.886)			0.248 (0.337)
Shear rate (/s)	SIT	-0.255 (0.324)			-0.271 (0.292)
	LIT		-0.056 (0.83)			0.064 (0.808)
	MIT			0.005 (0.986)			0.277 (0.282)
Blood flow	SIT	-0.127 (0.627)			-0.244 (0.345)
	LIT		0.111 (0.67)			0.102 (0.708)
	MIT			0.093 (0.722)			0.046 (0.861)

Note: The values are depicted as correlation (r) and significance values (p) in parenthesis.

Figure 3A. Correlation between the change in carotid artery functions and cognitive functions at the 4 th hour from the baseline during SIT intervention.

Though changes in reaction times and accuracy were found to be associated positively with change in carotid artery diameter (a, d), carotid artery velocity (b, e) and negatively associated with change in carotid artery shear rate (c, f ), the associations were not statistically significant.

Figure 3B. Correlation between the change in carotid artery functions and cognitive functions at the 4 th hour from the baseline during LIT intervention.

Though changes in reaction times and accuracy were found to be associated positively with change in carotid artery diameter (a, d), carotid artery shear rate (c, f ) and negatively associated with change in carotid artery velocity (b, e), the associations were not statistically significant.

Figure 3C. Correlation between the change in carotid artery functions and cognitive functions at the 4 th hour from the baseline during MIT intervention.

Though accuracy was found to be associated negatively with change in carotid artery diameter (d), carotid artery shear rate (f ) and positively associated with change in carotid artery velocity (e), the associations were not statistically significant. We observed non-linear and non-significant relation between reaction times and the central vascular functions (a, b, c) when compared 0 ^th and 4 ^th hour within conditions.

4. Discussion

Our present study aimed to investigate whether the change in the central vascular functions is associated with any change in the executive functions during the different active and passive work conditions. We found no significant relation exists between the change in carotid artery endothelial functions and the cognitive functions during the work conditions with or without interruption between varied intensities of physical activities.

Altered central vascular hemodynamics, especially carotid artery stiffness and sclerosis, is a long recognised risk for cognitive decline in the elderly. ³³ ^, ³⁴ Epidemiological studies have observed plausible mechanistic links for the altered carotid artery hemodynamics and cognition: narrowing of carotid artery due to atherosclerotic plaques and low shear stress reducing the bioavailability of nitric oxide and the prostaglandins, which in turn reduces the cortical perfusion to frontal, temporal, limbic systems and increased risk of cognitive and neurodegenerative disorders such as stroke and dementia. ³⁵ ^, ³⁶ Though the existing evidence has confirmed the positive association between central vascular functions and cognitive decline in the elderly, the association remains uncertain in young adults. As central vascular hemodynamic changes occur at an early, relatively younger age, the problem should be addressed at a younger age to mitigate the cognitive decline at an older age. However, our study failed to find a positive relation between the central vascular and cognitive functions in the young adults, probably due to homogeneity in the baseline characteristics (age, gender, diet and physical activity) with the simulated work conditions with or without physical activity interventions. Our study findings are contrary with the existing observational studies that have established the linear relation between the cognitive impairment and central vascular diameters ³⁷ flow velocity, ³⁵ ^, ³⁸ shear stress ³⁹ and blood flow. The findings of non-significant relation between the central vascular functions and the executive functions in our study probably due to the less age, gender bias, the nature of the working conditions (low stimulus, boredom) and unstandardized tasks not relevant to the participants routine work. ²⁸ ^, ⁴⁰ Further evidence to explore the association between cognitive functions and central vascular functions is warranted.

We found a 4.68% reduction in the carotid artery diameter after four hours of uninterrupted sitting. Our study findings concur with the recent experimental trials that have observed the reduction in central and peripheral artery diameter, reactivity and stiffness with uninterrupted sitting. ²⁸ ^, ³⁰ ^, ⁴¹ Further, our findings demonstrated an 8.68% increased shear stress in the carotid artery after four hours of prolonged sitting which is contrary to the existing hypothesis that prolonged sitting reduces stroke volume and increased shear stress in central and peripheral vasculature. ³¹ ^, ⁴¹ ^– ⁴⁴ Nevertheless, our findings concurs with the previous findings that prolonged sitting reduces the accuracy by 13%, whereas interrupting sedentary time with three minutes of stair climbing (MIT) every hour may improve accuracy by 3%. Even light-intensity walk breaks (LIT) could not mitigate the risk of inaccuracy associated with prolonged sitting. We could find a significant reduction (8-10%) in the carotid artery velocity and shear rate and reaction times when the prolonged sitting was with stair climbing (MIT). Our findings add to the existing evidence that demonstrated the short term effects of interrupting prolonged sitting to improve central vascular and cognitive functions. ²⁵ ^, ²⁸ ^, ⁴⁵ ^– ⁴⁷ However, we could not appreciate the association between central vascular and cognitive functions changes during various working postures and conditions.

4.1 Limitations

(1) Our findings are retrieved as a secondary analysis from a randomised controlled trial, and the sample size was based on the same. The readers should interpret the findings with caution due to the low sample and poor causal effect ⁴⁸; (2) Our study findings did not adapt postural changes (sitting to supine) for vascular function measurements, unlike earlier studies which might have influenced the results. We wanted to extrapolate the findings to the real-world work environment, and hence we have not altered the assigned position (sitting) during the carotid artery measurement ⁴⁹; (3) we have included only males for the convenience in central and peripheral vascular functions that inherently introduced a gender bias in our study. ⁴⁹ ^, ⁵⁰ Future studies should investigate the vascular effects of interrupting sitting among both genders for real-world generalisation.

To conclude, our study found no association between the change in the central vascular and cognitive functions during sitting with or without interruption. The negative effects in central vascular and cognitive functions associated with uninterrupted sitting can be well mitigated by a brief period of stair climbing hourly.

Data availability Underlying data

Harvard Dataverse. Alteration in carotid artery physiology and cognitive function during simulated work conditions in males. https://doi.org/10.7910/DVN/IP33PI. ⁵¹

This project contains the following underlying data: -

Alteration in the central vascular hemodynamics is speculated to influence cognitive functions, including executive functions in young adults. Prolonged sitting is associated with compromised central vascular functions, which activity micro-breaks could mitigate. However, the association between the carotid vascular hemodynamic alteration and the executive functions is yet to be explored. We administered a randomised controlled trial investigating the effects of various intensities' micro-breaks on central vascular and cognitive functions during simulated work conditions for four hours. The carotid artery hemodynamics and cognitive functions were measured by Duplex ultrasound at 0th, 2nd and 4th hour and computer-based Flanker tests at 0th, 1st, 2nd, 3rd and 4th hour of visit days, respectively. From the randomised controlled trial, we extracted the secondary data of carotid artery hemodynamics and cognitive functions change at the 4th hour from the baseline and analysed for any relation. Though we observed linear relation between the carotid artery hemodynamics and the executive functions, the relation was not statistically significant. we found a significant reduction in carotid artery diameter during prolonged sitting (0.03 cm [95%CI 0.01, 0.05]), velocity (10.35 cm/s [95%CI -2.85, 17.86]) and shear rate during interrupted sitting (174.39 [95%CI 65.67, 283.11]) We found increased accuracy during prolonged sitting (12.7% [95%CI 0.66, 24.81]) and sitting with light-intensity activity breaks (6.92% [95%CI 1.39, 12.44]). Though a significant relation between carotid artery function and cognitive function could not be established, micro-breaks can mitigate the vascular and cognitive risks associated with prolonged sitting.

Data are available under the terms of the Creative Commons Zero “No rights reserved” data waiver (CC BY 4.0 Public domain dedication).

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Reviewer response for version 3

Heffernan

Kevin S

1 Referee 1Columbia University, New York, NY, USA

Competing interests: No competing interests were disclosed.

5 3 2025

2025

This is an open access peer review report distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

recommendation

reject

This study examined the effect of interrupted sitting breaks on carotid hemodynamics and executive function. Overall, there were minimal changes in carotid hemodynamics and executive function with prolonged sitting with small effects of LIT and MIT. Overall, this is an interesting and somewhat well-designed study to examine the effect of LIT and MIT on carotid hemodynamics and executive function. Unfortunately, designing a study that does not address cultural barriers necessary to include women is a fatal study design flaw. This study should be re-done and designed in a culturally sensitive way to include both biological sexes. Also, as designed, this study cannot test the proposed study hypothesis. The narrative can be improved to improve overall readability and clarity. Below are additional specific comments.

General Comments

Abstract methods. Can you please operationally define carotid hemodynamics and what specifically was measured? Please also include information on sample (biologic sex, age) and sample size. Can you also offer more insight into study design? How many visits, what were the various “intensities” for the micro-breaks? As prepared, it is not clear what was done, what was measured, and who completed the tasks.

Abstract results. Please correct “We” sentence 2.

Based on the results presented in the abstract, the conclusion is not a logical extension. For example, authors state that there was increased accuracy with prolonged sitting. How, then, could microbreaks mitigate cognitive risks if there are no cognitive declines? Please consider revising conclusions to better align with study results.

Introduction. Last sentence, paragraph 1. Please contextualize the mixed findings. Briefly describe what was found according to the literature.

Introduction. Paragraph 2, sentence 1. Please revise “Mechanistic plausible mechanisms…” is redundant.

Paragraph 2. Please operationalize central vascular functions. What is meant by this term? Additionally, almost all of the references cited do not relate to studies on vascular function and cognitive function. There are now numerous studies that have examined the effect of sitting on endothelial function, arterial stiffness, carotid stiffness, cerebral hemodynamics etc and a few that have examined microbreaks and exercise snacks. Almost all references cited in paragraph 2 are review papers and not primary sources. The authors are encouraged to improve the rigor of the literature that this study draws upon.

Introduction Paragraph 3. Please clearly operationally define central vascular functions. Specifically, what will be measured and why?

The study design is not designed to test the study hypothesis. Please consider either revising the hypothesis to better match the study or develop a new study that is designed to test the hypothesis.

Please confirm that all participants provided written informed consent to participate in this study.

Study design, paragraph 2, last sentence. If this is a study purpose, then this should be included in the introduction.

The femoral artery is not a central artery. Moreover, lower limb blood flow is not mentioned in the introduction or study purpose (or results or discussion). Please clarify why this measure is being done and better integrate this measure into the paper.

“Due to cultural barriers…” is not clear. If this study was not designed to be culturally sensitive to ensure the inclusion of both men and women, that is a fatal study design flaw.

Based on study design, why not use a repeated measures analysis of variance and test for condition by time interactions?

Executive function was assessed 4 times for each condition. Please comment on the choice to focus on the 4 ^th hour measures. Justify this in the methods section.

Section 3.1. BMI. Please spell out abbreviations first time being used. How was height and weight measured to calculate BMI? This information is not provided in the methods.

Section 3.2. is difficult to navigate. Please pull the results apart. Focus on changes within a condition and then between conditions. Focus on one variable at a time.

The abstract states that there was an increase in accuracy with SIT, but table 2 shows a reduction (although the calculated change score is positive). Please clarify.

Table 2 is confusing. For example, if accuracy changed from 77 to 64, why is the change score shown as being positive? This obfuscates results.

The figures largely replicate the findings presented in Table 3 and are not needed.

The results for femoral artery measures are not presented.

Discussion paragraph 1. The authors conclude on carotid endothelial functions, but this was not specifically measured.

The final conclusion is challenging to interpret. This largely stems from conflicting reports of the effect of SIT on accuracy. The abstract states that accuracy increased, but the table shows a decrease (albeit the change score is listed as a positive change).

Is the work clearly and accurately presented and does it cite the current literature?

Partly

If applicable, is the statistical analysis and its interpretation appropriate?

Partly

Are all the source data underlying the results available to ensure full reproducibility?

Yes

Is the study design appropriate and is the work technically sound?

Are the conclusions drawn adequately supported by the results?

Are sufficient details of methods and analysis provided to allow replication by others?

Partly

Reviewer Expertise:

Vascular physiology, exercise physiology, effect of vascular function on cognitive function

I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above.

Kadavigere

Rajagopal

Kasturba Medical College, Manipal, India

Competing interests: None

6 3 2026

General Comments

Abstract results. Please correct “We” sentence 2.

The abstract states that there was an increase in accuracy with SIT, but table 2 shows a reduction (although the calculated change score is positive). Please clarify.

Response: We thank the reviewer for these detailed observations, all of which are well founded. We have comprehensively revised the abstract to address each point raised. Specifically: (1) carotid artery hemodynamics are now operationally defined, with the specific variables measured (diameter, blood flow velocity, shear rate) and the measurement tool (Duplex ultrasound) explicitly stated; (2) sample details are now provided, including biological sex, age range, sample size, and physical activity status; (3) the study design is now described clearly, including the number of visits, the crossover structure, the washout period, and the specific nature and intensity of each micro-break condition; (4) the change score direction error has been corrected throughout — the original abstract incorrectly reported increased accuracy during SIT, which arose from change scores being calculated as baseline minus hour 4 rather than hour 4 minus baseline; the corrected abstract accurately reports that accuracy declined during SIT; and (5) the conclusion has been revised to be a logical extension of the results — the original conclusion claimed micro-breaks could mitigate cognitive risks despite reporting no cognitive decline during sitting, which was internally contradictory; the revised conclusion accurately reflects what the data showed and is appropriately cautious about the absence of a significant vascular–cognitive association.

Introduction. Last sentence, paragraph 1. Please contextualize the mixed findings. Briefly describe what was found according to the literature.

Response: The sentence has been revised.

Introduction. Paragraph 2, sentence 1. Please revise “Mechanistic plausible mechanisms…” is redundant.

Response: We have rectified this.

Response: We have revised this paragraph.

Introduction Paragraph 3. Please clearly operationally define central vascular functions. Specifically, what will be measured and why?

Response: We have revised this paragraph.

The study design is not designed to test the study hypothesis. Please consider either revising the hypothesis to better match the study or develop a new study that is designed to test the hypothesis.

Response: We have rectified the study hypothesis.

Please confirm that all participants provided written informed consent to participate in this study.

Response: We confirm that all the participants provided written informed consent and mention in the revised manuscript.

Study design, paragraph 2, last sentence. If this is a study purpose, then this should be included in the introduction.

Response: This sentence is removed.

Response: We have revised this paragraph.

“Due to cultural barriers…” is not clear. If this study was not designed to be culturally sensitive to ensure the inclusion of both men and women, that is a fatal study design flaw.

Response: This limitation has been mentioned in the limitations sections and 2.2 participants.

Based on study design, why not use a repeated measures analysis of variance and test for condition by time interactions?

Response: We agree that a two-factor repeated-measures ANOVA with Condition (SIT, LIT, MIT) and Time as within-subject factors, with the Condition × Time interaction as the primary test, is the appropriate analysis for this crossover design and is substantially more rigorous than the paired t-test approach previously employed. The original analysis failed to fully exploit the repeated-measures structure of the data, discarded the hour-2 time point, and could not directly test whether the trajectory of change over time differed between conditions — which is the central experimental question.

We have revised Section 2.6 accordingly. All outcome variables have been re-analysed using rmANOVA, with Greenhouse-Geisser correction applied where sphericity was violated and Bonferroni-corrected pairwise comparisons used to follow up significant interactions. Table 2 and the Results narrative have been updated to reflect these analyses. The secondary correlational analyses examining the association between carotid hemodynamic changes and executive function changes within each condition have been retained but now incorporate Bonferroni correction for multiple comparisons.

We believe these revisions substantially improve the statistical rigour of the paper and we are grateful to the reviewer for directing us toward the more appropriate analytical approach.

Executive function was assessed 4 times for each condition. Please comment on the choice to focus on the 4 ^th hour measures. Justify this in the methods section.

Response: We acknowledge that focusing solely on the 4th hour change score for the vascular–cognitive association analysis, without justification, was an important omission in the original manuscript. We have revised Section 2.6 to explicitly justify this choice on three grounds: (1) carotid hemodynamics were only measured at hours 2 and 4, making hour 4 the only fully temporally matched time point available for the association analysis; (2) the existing literature supports 3–4 hours of uninterrupted sitting as the threshold at which vascular impairment becomes most pronounced, making hour 4 the most physiologically meaningful comparison point; and (3) pre-specifying a single time point for the association analysis limits inflation of Type I error across multiple comparisons. We additionally note that the revised repeated-measures ANOVA now captures the full trajectory of executive function change across all five time points, ensuring that the richness of the longitudinal cognitive data is not lost.

Section 3.1. BMI. Please spell out abbreviations first time being used. How was height and weight measured to calculate BMI? This information is not provided in the methods.

Response: We have spelled out body mass index (BMI) in full on first use in Section 3.1 and added units (kg/m²) throughout. We have also added a new subsection (2.3.3 Anthropometric measures) to the Methods detailing how height and body mass were measured and how BMI was calculated, including the equipment used, measurement conditions, and the WHO classification thresholds applied to characterise weight status. We apologise for the omission of these procedural details from the original manuscript.

Section 3.2. is difficult to navigate. Please pull the results apart. Focus on changes within a condition and then between conditions. Focus on one variable at a time.

Response: We agree that the original Section 3.2 was difficult to navigate, conflating multiple variables and conditions within a single paragraph. We have restructured the results into clearly delineated subsections, each addressing a single outcome variable. Within each subsection we first report changes within conditions (baseline to hour 4) and then address the between-condition comparisons via the Condition × Time interaction, before concluding with the vascular–cognitive association analyses. We believe this structure substantially improves the clarity and readability of the results.

Table 2 is confusing. For example, if accuracy changed from 77 to 64, why is the change score shown as being positive? This obfuscates results.

Response: The change scores in Table 2 were calculated as baseline minus hour 4, rather than the conventional direction of hour 4 minus baseline. This means that a positive value in the original table actually represented a decline in the outcome, and a negative value represented an improvement — the opposite of what a reader would intuitively expect and inconsistent with how the results were described in the text. We apologise for this error, which we acknowledge obfuscates the findings.

We have recalculated all change scores as hour 4 minus baseline throughout Table 2, so that a positive value now consistently indicates an increase from baseline and a negative value indicates a decrease. The direction of all effect size estimates (Cohen's d) has been corrected accordingly, and the Results narrative in Section 3.2 has been revised to ensure the direction of all reported changes is now accurate and consistent with the corrected table.

The figures largely replicate the findings presented in Table 3 and are not needed.

Response: We have removed the figures.

The results for femoral artery measures are not presented.

Response: The femoral artery data were collected as part of the parent trial protocol but fall outside the scope of the present secondary analysis, which is focused specifically on the association between central carotid hemodynamics and executive function. A justification for this scope decision and an acknowledgement of its limitations have been added to the Limitations section. The femoral artery data will be reported as part of the parent trial manuscript.

Discussion paragraph 1. The authors conclude on carotid endothelial functions, but this was not specifically measured.

Response: We agree that the original Discussion paragraph incorrectly characterised the findings as relating to carotid endothelial function, when in fact the study measured carotid artery hemodynamics — diameter, blood flow velocity, and shear rate — which are indices of the mechanical environment experienced by the endothelium rather than direct measures of endothelial vasodilatory capacity. We have revised the opening paragraph of the Discussion to accurately reflect what was and was not measured, explicitly acknowledging that conclusions regarding endothelial function cannot be directly drawn from these data. We have also noted that future studies should incorporate direct endothelial function measures, such as flow-mediated dilation, to address this limitation.

Response: The conclusion has been revised.