# Exploring social determinants of health in the context of metabolic and circadian influences on new hip fracture risk: longitudinal insights from CHARLS

## TL;DR

This study shows that better social conditions reduce hip fracture risk, especially in older Chinese people with metabolic and circadian issues.

## Contribution

The study reveals the combined impact of social determinants, metabolic syndrome, and circadian rhythm on hip fracture risk in China's elderly.

## Key findings

- Higher social determinants of health scores were linked to a 14% lower hip fracture risk.
- The protective effect of social factors was strongest in individuals with metabolic and circadian rhythm syndromes.
- ROC analysis showed strong predictive accuracy for hip fracture risk based on social determinants.

## Abstract

The risk of hip fractures is closely intertwined with social determinants of health (SDHs), metabolic factors, and circadian rhythm-related variables. Understanding the combined effects of these factors, particularly in the elderly population of China, has substantial public health implications.

This study utilized data from the China Health and Retirement Longitudinal Study (CHARLS, 2011–2020), which included 11,928 individuals aged 45 years and older, all free from a history of hip fractures. Kaplan-Meier survival curves, multivariable Cox proportional hazards models, and restricted cubic spline (RCS) analysis were applied to explore the associations between SDHs and hip fracture risk, stratified by metabolic syndrome (MetS) and circadian rhythm syndrome (CircS). Sensitivity analyses and receiver operating characteristic (ROC) curves were conducted to validate the findings and assess the predictive performance.

Higher SDHs scores were consistently associated with a reduced risk of hip fractures, particularly among individuals with MetS and CircS. For each unit increase in SDHs, the risk of first hip fracture was reduced by 14% (HR = 0.86; 95%CI, 0.77–0.95; P < 0.003). RCS analysis revealed a significant relationship between SDHs and the incidence of hip fractures across various metabolic and circadian rhythm subgroups (all P-values < 0.05, non-linear P > 0.05). Kaplan-Meier analysis demonstrated statistically significant differences in hip fracture incidence between SDHs groups (log-rank P < 0.001). ROC curve analysis demonstrated superior predictive accuracy for SDHs, with an AUC of 0.723 and 0.731, particularly among individuals with MetS and CircS.

SDHs are independently associated with a decreased risk of hip fractures, with a particularly pronounced effect observed in individuals with MetS and CircS. These findings underscore the critical importance of addressing both social and metabolic factors in the prevention of hip fractures, especially within aging populations.

The online version contains supplementary material available at 10.1186/s12889-025-25126-5.