Osteoporosis is recognised as a disease of mainly postmenopausal women, but decreased bone mineral density (BMD) and rapid bone loss can also occur in young adulthood, a disease often referred to as premenopausal osteoporosis. ¹ Attainment of peak bone mass in early adulthood represents a key factor in subsequent fracture risk, and inadequate skeletal development at this critical period could be a risk factor for osteoporosis later in life. ^{2– 3} A constellation of biological and lifestyle factors, including poor nutrition, sedentary behaviour, endocrine dysregulation, menstrual irregularities, gestational influences, and inadequate sun exposure, has been implicated in the diminution of BMD among young women. ^{4– 7} In clinical practice, a Z-score of −2.0 or lower is generally considered low for pre-menopausal women, especially when used in combination with other risk determinants. ⁷ Recent epidemiological studies show that low BMD is becoming more common in young women, especially in Asian populations; the prevalence of reduced BMD in young Asian women between the ages of 20–40 years may already reach 15–30 percent. ^{8– 9} These findings highlight the increasing public health concern of early skeletal health evaluation and the need for the identification of modifiable determinants during the peak bone building period. ⁸ Quantitative ultrasound (QUS) has become a pragmatic, cost-effective and radiation-free modality for community-based skeletal screening, particularly in resource-constrained settings. ¹⁰ Multisite instruments, for instance, the Omnisense, assess bone properties at peripheral skeletal sites and show reasonable concordance with dual-energy X-ray absorptiometry in identifying persons with decreased BMD. ^{10, 11} Although QUS is not a replacement for diagnostic imaging, it is sufficiently portable and feasible to be used for large-scale epidemiological studies and early risk identification. ^{10, 12} Moreover, community and cohort data from South Asia today show that women at reproductive age often have low BMD with the associated high rate of vitamin D insufficiency and inadequate calcium intake, which may impair peak bone mass and increase the risk of long-term fracture. ^{13– 15} Consequently, multisite QUS has been gradually used in field-based epidemiological screening, due to its portability, affordability, and acceptable concordance with conventional densitometric methods, but has been defined as a screening rather than a diagnostic tool. ¹¹ In spite of the growing body of evidence from around the world, community-based studies on low BMD in young Indian women are still limited, particularly those that incorporate nutritional, reproductive, lifestyle and psycho-social determinants in a coherent analytical framework. ^{8, 10, 11} Existing research in India has mainly focused on postmenopausal cohorts or reference BMD databases, without comprehensive risk factor evaluations in younger women. ^{15, 16}

Therefore, the present study was conducted to determine the prevalence of low bone mineral density and identify its associated risk factors among Indian women aged 20–40 years using multisite quantitative ultrasound in a community-based cross-sectional design.

A total of 1,350 women were screened, of whom 1,176 participants met the inclusion criteria and were retained in the final analysis to find the prevalence of low bone mineral density conditions in the age group of 20–40-year-old women in the population of Punjab ( Figure 1).

For statistical analysis, the participants were categorized into three groups: normal (z score ≥ −2.0), z score < −2.0 and ≥ −3.0, and z score < −3.0.

Table 1 shows the baseline characteristics of the women participants. Both z-score categories had similar mean ages (~33 years). The mean values of anthropometric covariates (weight, waist circumference, waist: hip ratio) were higher in women having a z-score < −3.0. Further, in terms of obstetrics and gynecological covariates, the average menarche age was almost similar (~13 years) in all three groups. Significantly greater number of pregnancies (3.94), children (2.39), and prolonged duration of breastfeeding (14.41 months) was reported from women belonging to the z-score below −3.0 category in comparison to the normal group. In addition, significantly low mean physical activity level (488.41 METS-min/week), low sun exposure index (0.83), and high perceived stress (PSS) (25.67) were reported from women in the category of z score below −3.0 (p < 0.025). Moreover, women in the category of z score below −3.0 had significantly low mean SOS values of radius (3743.65 m/s) and tibia (3903.18 m/s), and low SES when compared to the mean values of the normal group (p < 0.025).

The results in Table 2 revealed that 83.9% of the participants had high waist circumference. 32.48% of the women from the total sample population had a complaint of low back pain. Out of 1176 women studied, 13 women had undergone the oophorectomy procedure; of them, 53.84% of the women had a z-score below −3.0. No woman had reported having undergone hormonal therapy. Only 0.5% of the women mentioned the history of osteoporosis as their medical history. 7.57% of the women reported rheumatoid arthritis as their medical history; of them, 71.15% of the women had z scores less than −2.0. 27.72% of the total sample population reported having more than 3 children, of which 41.71% of the women had a z-score < −2.0. Further, 9.27% of the women surveyed reported having consumed calcium supplements (minimum 2 months continuously); of them, 77.98% were in the normal category (Table-2).

The current study revealed that low and very low bone mineral density (BMD) is a significant concern in young Indian women, underscoring the importance of early skeletal health assessment. Consistent with previous studies, later age at menarche, limited sun exposure, low dietary calcium intake, parity, and hypothyroid status were significantly associated with low BMD. Given the cross-sectional design of this research, these associations cannot be interpreted as causal; however, they align with biological plausibility and existing evidence. Similar prevalence trends have been reported in other Asian populations, with low BMD observed in 20–26% of Vietnamese premenopausal women ¹⁴ and 18–22% of Chinese cohorts. ¹⁷ In the present study, nearly one-third of the participants demonstrated compromised bone health, emphasizing the need for routine screening and preventive measures in young adult women. ^{18, 19} European studies reported lower rates, possibly due to higher dietary calcium intake and more structured physical activity. ^{20– 22} These findings contribute to the growing consensus that low BMD is not confined to postmenopausal women but is increasingly relevant in younger populations.

Since the sample size was large and to simplify the data grouping for statistical computation, the data was divided into two categories: z scores below −2.0, ²³ as having low bone mineral density, and z score below-3.0 has very low bone mineral density, for women who had not attained their menopausal status were used using QUS. The prevalence of low bone mineral density, categorized as z-score below −2.0 and z- score below −3.0, was found to be 22.6% and 8.1%, respectively. Our study results showed a higher prevalence (8.1%) of low bone mineral density (z score below −3.0), whereas a large sample-sized QUS study based on Vietnamese women of a similar age group showed a prevalence of osteoporosis as 3.9%. ²⁰ The current study results also suggest that, on average, every third woman surveyed had low bone mineral density.

Numerous studies have suggested various factors are responsible for low bone mineral density conditions using the QUS technique. ^{19, 20, 24} In the current study, analysis of the adjusted regression model revealed that an increased number of pregnancies (>3) and late menarche (>14 years) appeared as significant risk factors for low bone mineral density conditions. The results showed 45.3% of the women surveyed had a history of more than 3 pregnancies, of which 86.65% had low SOS values. Further, 63.77% of the women had a late onset of menarche (>14 years), and 35.6% of women had breastfed for more than a year. It is known that late menarche, multiple pregnancies, and prolonged lactation period in the absence of adequate calcium intake result in decreased BMD levels. ^{25– 28} Further, it is to be noted that no woman participant was pregnant nor breast-feeding at the time of the study. All women surveyed had recorded their last lactation period 6–9 months before at the time of investigation, which is sufficient time for the bone loss to recover post-weaning. ²⁹ Our findings are consistent with recent studies reporting rising prevalence of low BMD among younger women in South and East Asia, emphasizing the importance of early screening in this population. ¹⁶

A notable finding in this study was the presence of several young women who had undergone hysterectomy or oophorectomy at an unusually early age. Although these procedures were not significant predictors in the regression analysis, their occurrence raises concerns about the reproductive health status of young women. Most affected participants belonged to rural communities and had undergone these surgeries following pregnancy-related complications. This pattern aligns with national reports showing that early marriage, poor nutrition, and limited access to quality maternal healthcare contribute to higher gynaecological morbidity in rural India. ¹³ Prior studies also highlight that many women undergo hysterectomy or sterilization without adequate counselling and may not even be aware of whether their ovaries were retained. ¹⁸ These observations underscore the need for better reproductive health awareness, improved counselling, and access to conservative treatment options in rural regions.

Further, it was observed that 69.04% had high perceived stress. Increased stress levels are known to be related to osteoporosis. ³⁰ Increased monetary expenses owing to rapid economic growth, poor spousal relations causing physical abuse, especially among rural women, were cited as possible causes for their increased stress levels. Thus, high perceived stress scores were found to be a significant risk factor for low bone mineral density status of women.

Another notable observation found in the study was the increased prevalence of central obesity (WC > 80 cm) in the studied women. The results showed that 86.39% of the women had high WC, of which 50.39% of the women had low bone mineral density scores. High fat intake could be one of the possible reasons for this obesity, as 98.99% of the women surveyed had excess of fat intake in their diet. ³¹ These figures suggest that the main form of meeting the calorie demands is through increased fat intake. Rapid urbanization and a changing economy might have stimulated these habits, as a high-fat and high-sugar diet is cheaper than healthy foods. ³² In addition, we also found increased mobility and physical activity levels reflected as a significant protective factor against low bone mineral density conditions (p < 0.001). It was observed that 55.95% of the women surveyed were physically active, that is, they expended 600 METS/min-wk. But no women were reported to be in the “Active” category (meeting the minimum criteria of expending 3000 METS-min/wk). ³³ Moreover, the majority (75.09%) of the women surveyed had optimal sun exposure, suggesting that in spite of social and cultural limitations posed on Indian women, the traditional habit of sitting in the sunlight still exists. The results of the current research correspond to the existing literature that records bone-related issues at the early ages in young women living in Asian and low-middle-income countries. Emerging factors in low BMD in younger women younger than 40 years have been pointed out by modern research due to nutritional deficiencies, lifestyle habits, and late reproductive maturation. ^{34, 35} These similarities support the utilization of bone health assessment as a priority area of concern in reproductive-age populations.

An additional goal of the study was to observe the role of micro and macronutrients in bone health. It is known that a sufficient amount of calcium and other nutrients play a vital role in maintaining good bone health status. ³¹ In the current study, analysis of nutrient intake through the 24-hour dietary recall method showed low calcium levels posed as an independent risk factor for low bone mineral density conditions among women(p < 0.001). Further, all major and micro nutrients (protein, folic acid, niacin, riboflavin, β-carotene, vitamin B12, and zinc) assessed did not meet the recommended dietary levels, which may lead to several multiple nutritional deficiencies. Also, deficiency of vitamin A and iron, which is viewed as a well-recognized problem in Indian women (WHO, 2010) was prevalent in the current study as well. ³²

The present study presents the prevalence of low bone mineral density status in young women of Punjab using a validated multisite QUS technique. Our results show that there is an increased prevalence of low bone mineral density in these young women. A multiple logistic regression model assessed associations between various factors and low SOS. Our study strongly advocates the need to propagate effective preventive measures (increased physical activity and healthy dietary habits) and educate women to improve bone health on a large scale, as most of the women are unaware of the importance of these healthy practices in building healthy bone status.

The study was conducted in line with the Declaration of Helsinki for human participants and approved by the Institutional Ethics Committee, Faculty of Sports Medicine and Physiotherapy, Guru Nanak Dev University, Amritsar (No-1319/SMP). This study is registered with the Clinical Trial Registry of India (CTRI/2015/10/006240).

Written informed consent was taken from all participants for their voluntary participation in the study before data collection, explaining the possible use of the data for research and publication without revealing their identity.