Association between sunshine duration and hospitalization risk for mental and behavioral disorders in Zigong City, Sichuan Province

BackgroundSunshine duration is closely associated with population mental health and emotional states, although its relationship with mental and behavioral disorders (MBD) remains insufficiently studied.ObjectiveTo analyze the effect of sunshine duration on hospital admissions for MBD in Zigong City, Sichuan Province.MethodsHospital admission records for MBD from 10 medical institutions, meteorological data, and ambient air pollutant concentrations were collected in Zigong City from January 1, 2019 to December 31, 2024. A distributed lag non-linear model (DLNM) was employed to calculate single-day and cumulative lag effects of different sunshine duration exposures—0 h (P0, P5, P25), 6 h (P75), and 10.4 h (P95)—on hospitalization risks for MBD, stratified by diagnostic category, sex, and age groups. ResultsThis study analyzed 36597 hospital admissions for MBD in Zigong City. The exposure-response curve for sunshine duration at lag 0 d exhibited an inverted N-shaped pattern, with minimum relative risk (RR) of hospitalizations observed at 14 h sunshine duration. The immediate effects of different levels of sunshine duration on the hospitalization risk for MBD, schizophrenia, schizotypal and delusional disorders (SSDD), and neurotic, stress-related and somatoform disorders (NSSD) were significant, with the cumulative effect peaking at lags 12–13 days. For extremely short sunshine duration 0 h, the maximum relative risk (RR) values (with 95% confidence intervals, 95%CI) of hospitalization risk were 1.209 (1.001, 1.459) at lag 1 d for SSDD patients and 1.398 (1.133, 1.724) at lag 0 d for NSSD patients, respectively. The cumulative effect on hospitalization risk induced by short sunshine duration 6 h was higher than that induced by extremely short sunshine duration 0 h and long sunshine duration 10.4 h. Among populations stratified by gender and age, male patients and those aged over 70 years had higher hospitalization risks. For short sunshine duration 6 h, the cumulative RR (CRR) value (95%CI) of hospitalization risk for male MBD patients was 3.373 (1.362, 8.358) at cumulative lag 0–12 d, which was higher than that for female patients [2.943 (1.471, 5.889) at cumulative lag 0–13 d]. The population aged over 70 years was more sensitive to single-day and cumulative lag effects on hospitalization risk than other age groups. For short sunshine duration 6 h, the RR and CRR values (95%CI) of single-day and cumulative lag effects on hospitalization risk were 1.336 (1.002, 1.783) at lag 0 day and 5.085 (1.680, 15.392) at cumulative lag 0–12 d, respectively. At lag 13 d, long sunshine duration 10.4 h exposure was associated with depression hospitalizations in patients <20 years with RR=1.127 (95%CI: 1.002, 1.270).ConclusionWhen the daily sunshine duration is less than 14 h, it will increase the hospitalization risk of MBD in the population to varying degrees, with both single-day and cumulative lag effects. It is recommended that the public, especially vulnerable groups such as people with MBD aged 70 years and above and those with depression under 20 years, strengthen health protection to reduce the health risks caused by changes in sunshine.