Interplay of age, gender, education, and heart rate in dementia among older adults in Wakiso, Uganda: a cross sectional study

Hypotheses

We hypothesised that there exists a noteworthy association between aging and an increased risk of Mild Cognitive Impairment (MCI) and dementia, such that the likelihood of these conditions ascends with each ensuing year of life. Moreover, we contend that sex plays a complex role in cognitive decline, wherein being male could offer a protective effect against MCI and dementia. In addition, we anticipated that a higher level of education serves as a protective factor against MCI, as per the cognitive reserve hypothesis; however, the relationship between education levels and dementia risk might be less direct. Lastly, we suspect that elevated heart rates may indicate a heightened risk of both MCI and dementia, highlighting the potential connection between cardiovascular health and cognitive well-being in the older adult population of Wakiso, Uganda.

Study design and setting

This cross-sectional study was conducted in Wakiso District of Uganda, a region characterised by its diverse demographic composition, including urban, suburban, and rural areas, and hosts a population of approximately two million residents. Our research specifically targeted older adults, aged 65 years and above, from three sub-counties: Nansana, representing urban settings, and Busukuma and Nakwero, illustrating rural environments.

Participants

A purposive sampling approach was adopted to select 106 individuals aged 65 years or older from designated sub-counties in Wakiso, Uganda, including Nansana, Busukuma, and Nakwero. The selection process was focused on individuals diagnosed with Alzheimer’s disease and related dementias (ADRD). The assistance of Village Health Teams and local council leaders was utilized to identify households with known ADRD patients. The selection process was designed to exclude critically ill participants from the study. A total of 140 homesteads were approached, resulting in a 75% response rate. The criteria for participation included being a resident of the targeted sub-counties, aged 65 years or older, and had a diagnosis of dementia. Informed consent was obtained from all participants, ensuring they had a comprehensive understanding of the study’s objectives, procedures, potential benefits, and associated risks. For participants who were unable to provide informed consent personally, verbal consent accompanied by written consent from their caregivers was obtained. Ethical considerations were of paramount importance throughout the study, with informed consent obtained from all participants directly or from their proxies when necessary, ensuring voluntary participation and understanding of the study’s objectives and procedures. The study protocol was thoroughly reviewed and approved by the School of Biomedical Sciences Research and Ethics Committee at Makerere University, with approval number SBS-2022-256 and formal approval date of May 2, 2023, guaranteeing compliance with the highest ethical standards for research involving human participants. Additionally, the study’s protocols received accreditation from the Uganda National Council for Science and Technology, with reference number HS2930ES.

Data collection procedures

A team of experienced research assistants with backgrounds in community psychology, social work, and nursing oversaw the data-gathering process. The team administered questionnaires from May to July 2023, which typically took 90–120 min to complete. All sessions were conducted in Luganda, the most common local language, to ensure clear communication. Before starting the data collection, each potential participant was approached individually to explain the purpose, nature, potential benefits, and risks of the study. Participants were informed that their participation was voluntary and that they had the right to withdraw without consequences. Written informed consent was obtained from the participants who were willing and able to provide consent after confirming their understanding and comfort, which included a clause explicitly stating that the results of the study may be published. For those unable to provide written informed consent, verbal consent was secured, accompanied by written consent from their caregivers, who also acknowledged and consented to the potential publication of study findings. The data were stored securely, ensuring limited access to authorized personnel and maintaining the anonymity and privacy of the participants.

Data sources/measurements

Sociodemographic details, including age, sex, educational background, occupation, comorbidities, marital status, previous illnesses, and concomitant medication, were collected through a brief questionnaire. A case report form was used to gather information pertaining to previous medical illnesses, concomitant medications, heart rate, blood pressure, body mass index, and musculoskeletal (MSS) examination. The Montreal Cognitive Assessment Tool (MoCA) (copyright permission to use obtained) was employed to screen for dementia and has been validated for use in an African setting (Beath, Asmal, van den Heuvel, & Seedat, 2018). A score of 23 or lower indicated normal cognition, 19–24 indicated mild cognitive impairment, and <19 indicated dementia.

Bias

Several measures were implemented during the research process. First, purposive sampling was used to ensure a representative sample of individuals aged ≥65 years diagnosed with Alzheimer’s disease and related dementias (ADRD) within the specified sub-counties of Wakiso, Uganda. This targeted approach helped mitigate the selection bias by focusing on specific demographic and health conditions relevant to the study objectives. Additionally, collaboration with Village Health Teams and local council leaders in identifying potential participants helped achieve a more comprehensive and less biased selection of individuals with known ADRD conditions.

To further reduce information bias, experienced research assistants with backgrounds in community psychology, social work, and nursing were employed to administer the questionnaires and conduct assessments. The use of the Montreal Cognitive Assessment Tool (MoCA), a validated instrument for dementia screening in an African setting, improved the reliability and consistency of cognitive health evaluations among participants.

Informed consent procedures were followed, with participants (or their caregivers in cases where individuals were unable to consent) thoroughly briefed about the study’s purpose, procedures, potential benefits, and risks. This ensured that the participants were fully informed and voluntarily agreed to participate, thus minimizing the risk of coercion or misunderstanding.

Moreover, detailed collection of sociodemographic data, including age, sex, educational background, and health parameters, allowed for a comprehensive analysis of potential confounding factors. Statistical analyses, including multivariate logistic regression, were utilized to adjust for these confounders, further minimizing bias and elucidating the independent effects of age, sex, education, and heart rate on dementia and MCI risk.

Study size

To determine the sample size for our study, which focused on trends in heart rate, we adhered to the standard formula for sample size calculation in quantitative research. The key parameters defined for this calculation included the standard normal variate (Zα/2) representing the z-score at a 5% type I error rate (significance level), and absolute precision (d), set at 2 beats per minute (bpm). Furthermore, we based our estimation of the standard deviation (SD) in the existing literature, adopting a value of 11 bpm as a representative measure of heart rate variability in the target population. Incorporating these parameters into the formula yielded a minimum sample size of 106 older adults. This calculation ensured that the study was adequately powered to detect meaningful trends in heart rate within the specified error and precision limits.

Data management and statistical analysis

A formal analysis of sociodemographic attributes was conducted using frequency distributions, and gender-based differences were examined using the chi-squared test. The Mann-Whitney U test was used to investigate age-related disparities by sex. Our study examined the interplay between age, sex, education, and heart rate in relation to dementia and mild cognitive impairment (MCI) in an older adult population in Wakiso, Uganda. Wakiso. The outcome variables were age, sex, heart rate, formal education duration, previous medical illnesses, and concomitant medication use. Multivariate logistic regression analyses were performed to explore the relationships between various factors and outcomes, and both crude and adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated to identify the strength and orientation of these associations. Statistical significance was set at p < 0.05, and all analytical procedures were performed using the Stata 17.

Overall sample description

The study involved a sample of 106 individuals, comprised of 76 individuals with dementia, 15 with mild cognitive impairment, and 15 healthy participants. Of these, 83 were female (78.3%), with a median age of 75 years (interquartile range: 70-82). A comprehensive breakdown of the participants’ demographics can be found in Table 1. The participants’ median education level was 3 years (interquartile range: 1-6). Approximately 20 (18.9%) were taking concomitant medications, such as antidiabetic and antihypertensive drugs. Most participants had a preexisting medical condition, with 79 (74.5%) reporting such an issue. With respect to comorbidities, 15 (14.1%) had hypertension, while 19 (19.9%) had musculoskeletal diseases.

Results of the multivariate logistic regression analysis

Table 2 presents the results of a multivariate logistic regression analysis examining the interplay of age, gender, education, and heart rate in relation to the risk of developing MCI and dementia. The study found that for every year increase in age, the risk of developing MCI and dementia increased by 1.19 (95% CI 1.04;1.38, p=0.015) and 1.22 times (95% CI 1.07;1.40, p=0.003), respectively. In terms of gender, males had an increased risk of dementia (0.14, 95% CI 0.03;0.81, p=0.028), while male sex was associated with a reduced risk of MCI (0.17, 95% CI 0.02;1.38, p=0.097). Education was found to be a significant protective factor, reducing the risk of MCI by 28% for each additional year (a relative risk reduction of 0.28, 95% confidence interval of 0.15-0.55, p<0.001). However, the relationship between education and dementia was unclear (relative risk reduction 0.72, 95% confidence interval of 0.52-1.01, p=0.053). Individuals with high heart rates had a 13.3 times higher risk of MCI and an 11.66 times higher risk of dementia, with statistically significant results (p-values of 0.013 and 0.004, respectively). The 95% confidence intervals range from 9.72 to 19.62 and 8.16 to 15.21, respectively, indicating a strong relationship.

Limitations

Addressing these limitations in future research could involve implementing longitudinal study designs, expanding the range of cardiovascular and lifestyle-related variables examined, employing more diverse and representative sampling methods, and conducting similar studies in various cultural and geographical settings to enhance the generalizability of the findings.