COVID-19 status: association with outdoor light exposure and meal timing, independent of chronotype

The influence of lifestyle factors, such as light exposure and meal timing, on susceptibility to infectious diseases like COVID-19, remains an area of active investigation. This cross-sectional study analyzed self-reported data from 1147 healthy adults (aged 18–65 years), divided into COVID-19 negative (n = 797) and positive (n = 350) groups. Data collected were MEQ chronotype score, MCTQ (including outdoor light exposure (OLE), bedtime, mid-sleep, wake-up) and meal timing on work-days and free-days. Compared to COVID-19 positive participants, individuals who remained COVID-19 negative reported greater weekday OLE (+39 minutes, p = 0.006) and earlier mid-sleep on working days (9 min, p = 0.031). They also exhibited earlier latest meal timing on workdays (26 min, p = 0.016) and free-days (27 min, p = 0.015), and earlier main meal timing on free days (21 min, p = 0.025). Multivariate analysis corrected for age, sex, BMI and MEQ identified higher weekday OLE (β = 0.103, p = 0.001), earlier mid-sleep on workdays (β = 0.080, p = 0.010), and earlier main meal timing on free days (β = 0.065, p = 0.037) as independent predictors of COVID-19 negative status. This study suggests that greater OLE, earlier mid-sleep on workdays and earlier main meal timing, may be independently associated with a reduced risk of COVID-19 infection in healthy adults, underscoring the importance of circadian health in infectious disease susceptibility.