Association between ambient temperature and psoriasis in Foshan, China: a time series analysis

Psoriasis is a recurrent chronic inflammatory disease by recurrence. Although considerable research has examined the relationship between ambient temperature and psoriasis, findings remain inconsistent. We conducted a retrospective cohort study in Foshan, China, using a distributed lag nonlinear model (DLNM) to investigate the relationship locally. We identified a W-shaped relationship between temperature and psoriasis incidence in Foshan, with both extreme low temperature (ELT) and extreme high temperatures (EHT) significantly increasing risk. After adjusting for particulate matter pollution as a confounder, ELT exposure showed the strongest single-day lagged effect on psoriasis onset at lag 2 (relative risk [RR] = 1.349; 95% confidence interval [CI]: 1.090-1.671). The cumulative lag effect for ELT peaked at lag 4 (RR = 1.761, 95% CI: 1.141-2.716), while EHT exposure reached its peak cumulative lag effect at lag 0 with RR = 1.165 (95% CI: 1.008-1.346). After adjusting for gaseous pollutants as potential confounders, ELT exposure showed the strongest single-day lagged effect at lag 2 (RR = 1.404; 95% CI: 1.128-1.746), and exposure to EHT demonstrated its peak cumulative lag effect at lag 0 (RR = 1.180; 95% CI: 1.018-1.369). Subgroup analyses further revealed that males were more susceptible to temperature fluctuations. Based on these findings, we conclude that temperature fluctuations significantly impact psoriasis in this region.