A prospective cohort study was conducted in 285 community-dwelling older adults from December 2016 through to May 2019. Individual household indoor environment data and ARI incidence were continuously collected. A time-stratified case-crossover analysis was conducted to estimate the excess risk (ER) of ARI associated with per unit increase of daily mean indoor temperature, relative humidity (RH) and absolute humidity (AH).
Lower indoor AH in household was associated with a higher risk of ARI in the community dwelling older adults in Hong Kong during cold season.
In total, 168 episodes of ARI were reported with an average risk of 36.8% per year. We observed a negative association of ARI with indoor AH up to five lag days in cool season, with a 6-day cumulative ER estimate of -9.0% (95% confidence interval: -15.9%, -1.5%). Negative associations between household temperature or RH and ARI were less consistent across warm and cool seasons.
Ambient environmental factors have been associated with respiratory infections in ecological studies, but few studies have explored the impact of indoor environmental factors in detail. This study aimed to investigate the impact of indoor environment on the risk of acute respiratory illness (ARI) in a subtropical city.