The association between apparent temperature and psoriasis outpatient visits: a time-series study in Hefei, China

Temperature may be an important environmental factor affecting psoriasis. This study aimed to determine the potential association between apparent temperature (AT) and outpatient visits for psoriasis in Hefei, China. Daily psoriasis clinic visits in Hefei were collected from January 1, 2016 to December 31, 2020. A Poisson generalized linear regression model (PGLM) combined with a distributional lagged nonlinear model (DLNM) was used to analyze the impact of AT on psoriasis outpatient visits; the model was adjusted for relative humidity, wind speed, precipitation, PM2.5, NO2, SO2, time trends, Sundays, and holidays. The analyses were stratified by age and sex. A total of 24,351 patients with psoriasis were included in this study. Only a low AT showed a delayed and strong risk effect. Referring to the median AT (16.8 degrees C), the effect of low AT started at lag 2 days and showed an increasing and then decreasing trend for approximately 5 days; the effect of extreme cold (1st percentile) and cold (5th percentile) peaked at lag 4 days with a relative risk (RR) of 1.117 (95% CI:1.065 to 1.171) and 1.081 (95% CI:1.044 to 1.119), respectively. The effect of mild cold (25th percentile) reached a maximum RR of 1.033 (95% CI:1.017 to 1.048) at lag 6 days. Subgroup analysis showed that low AT risk was more pronounced and longer-lasting in men and individuals aged <45 years. Our study provides evidence that a low AT increases the risk of psoriasis. Men and young people are vulnerable to potential adverse effects. There is a need for enhanced health interventions, medical care, and early warnings for patients.