Short-term effect of sunshine duration on daily emergency visits for hip fractures in Beijing, China: a time-series study

This study employs a time-series analysis to investigate how sunshine duration associates hip fractures in China and found both short and long durations of sunshine increased the risk of hip fractures. The findings can guide strategies for reducing hip fractures and enhance health education on fracture prevention. Background Studies on the associations between sunshine duration and emergency visits for hip fractures (HF) are limited. This study aimed to assess the short-term effect of sunshine duration on the risk of emergency visits for HF. Methods Daily emergency visits for HF at Beijing Jishuitan Hospital from 2015 to 2019 and contemporaneous meteorological and air pollutant data were collected. A Poisson generalized linear regression model combined with a distributed lag non-linear model was applied to analyze the lag-exposure-response relationship between sunshine duration and HF. Stratified analysis was performed by gender and age. Results A total of 10,874 cases were identified. The overall cumulative exposure-response curve showed a U-shaped relationship between sunshine duration and HF. With 7.2 h as the reference (lowest HF emergency visit risk), significant single-day effects of short sunshine duration (0 h, 2.5th percentile) were observed from the 11th to the 13th day, peaking on lag day 13 (RR = 1.033, 95% CI: 1.003-1.065), while its cumulative effects lasted from lag days 0-11 to 0-14, with the highest RR of 1.327 (95% CI: 1.088-1.619) at lag day 0-14. Significant single-day effects of long sunshine duration (12.7 h, 97.5th percentile) occurred from the 10th to the 12th day, peaking on the 12th day (RR = 1.030, 95% CI: 1.000-1.061), but no cumulative lag effects were found. This U-shaped pattern was consistent across subgroups, especially among female patients and those aged 66-79 years; conversely, the risk of HF-related emergency visits decreased with increasing sunshine duration in patients aged 40-65 years with a relatively high uncertainty. Conclusions Both short and long durations of sunshine are associated with an increased risk of HFs emergency visits. Females and patients aged 66-79 years might be more vulnerable to short sunshine duration.