Lifestyle clusters and bone mineral density in Chinese adults: a cross-sectional study with cluster analysis

Osteoporosis is a major global public health challenge, with lifestyle as a key modifiable factor. This study aimed to examine associations between lifestyle patterns and bone mineral density (BMD) in Chinese adults.

In this cross-sectional, multi-center study, 5,324 adults from Beijing (2016-2020) with complete lifestyle questionnaires were analyzed (lumbar spine BMD available for 4,028; hip BMD available for 4,654). Each of eight lifestyle variables was residualized on age and sex before k-means clustering (k = 3) categorized participants into three groups: office/mental-labor workers with low leisure-time activity (OL), physical-labor workers (PL), and office/mental-labor workers with an active leisure-time lifestyle (OA). Differences in lumbar spine and hip BMD among clusters were examined using multivariable-adjusted models (age modeled via restricted cubic spline, sex, body mass index [BMI], hospital fixed effects), with stratification by sex, age group, and BMI group, alongside full-cohort dose-response and cluster × exposure interaction analyses.

After adjustment, the OA cluster showed higher lumbar spine BMD than the OL cluster (adjusted difference = 0.024 g/cm², 95% CI 0.012-0.036, P < 0.001). The PL cluster showed lower hip BMD than both the OL cluster (adjusted difference = -0.041 g/cm², 95% CI -0.056 to -0.027, P < 0.001) and the OA cluster (adjusted difference = 0.028 g/cm², 95% CI 0.011-0.044, P = 0.002), despite the occupational physical activity inherent to manual labor. These associations were broadly consistent across sex, age, and BMI strata, though attenuated among participants aged ≥70 years and those with obesity. In dose-response analyses, exercise and sun exposure showed non-linear associations with BMD at both sites, while calcium supplementation frequency showed a consistent negative linear association that did not vary by cluster.

A lifestyle pattern combining active leisure-time behavior with office-based occupation was associated with higher lumbar spine BMD, while an occupationally physical-labor lifestyle was associated with lower hip BMD relative to both other clusters. These associations exhibited site-specific patterns and were generally consistent across demographic subgroups. Given the cross-sectional design, these findings should be interpreted as associations rather than causal effects; prospective studies are needed to clarify their causal structure and clinical significance.