Supplementary file 1_Lifestyle factors or protective behaviors: which are more strongly associated with upper respiratory tract infections after COVID-19? A cross-sectional study of 1,535 Chinese college students.docx

Hierarchical negative binomial regression was used. Demographic variables were entered in the baseline model, after which lifestyle factors and protective behaviors were added sequentially. Their entry order was then reversed to compare the relative contribution of each variable group.</p>Results<p>When entered first into the baseline model, lifestyle factors produced a greater improvement in model fit than did protective behaviors (Δχ²/df, 7.34 vs. 2.48; AIC, 4981.4 vs. 5067.9).

Female sex, higher BMI categories, chronic diseases, COVID-19 vaccination ≥2 doses, daytime sleepiness (IRR, 1.768–2.324), sedentary, vigorous-intensity physical activity were associated with more URTI episodes, whereas sleep duration of at least 7 h and moderate-intensity physical activity were associated with fewer episodes (all p < 0.05). Among protective behaviors, only natural ventilation showed a consistent inverse association (IRR: 0.425–0.475; p < 0.05).

Most other behaviors, including handwashing before meals, maintaining 1 m distance, avoiding touching the eyes/mouth/nose and public surfaces, and disinfecting phones and keys were not significantly associated with URTI episodes.</p>Conclusion<p>Lifestyle factors were more strongly associated with URTI episodes than protective behaviors among college students in the post-COVID-19 period. These findings suggest that modifiable lifestyle factors, including sleep, physical activity, and sedentary behavior, as well as natural ventilation, may be relevant targets for campus health strategies.</p>