Spatiotemporal relationship between temperature and non-accidental mortality: Assessing effect modification by socioeconomic status

Background: Most published studies have assessed the overall health impact of temperature by using one-station or multiple-station averaged meteorological and air quality data. Concern has arisen about whether the temperature health impact is homogeneous across the whole territory geographically, since green space and socioeconomic factors may modify the impact. Objective: This study aims at investigating how small-area mortality is modified by local temperature and other meteorological, air quality, green space, and socioeconomic factors of small geographic units in a subtropical urban setting. Methods: Data on meteorological, air pollutants, and non-accidental mortality count in Hong Kong during 2006-2016 were obtained. Combined with green space and socioeconomic data, spatiotemporal analysis using Generalized Additive Mixed Models was conducted to examine the temperature-mortality relationship, adjusted for seasonality, long-term trend, other meteorological factors, pollutants, socioeconomic characteristics and green space. Results: Socioeconomic status was found to modify the temporal temperature-mortality relationship. A J-shape association was identified for most areas in Hong Kong, where a sharp increase of mortality was observed when daily minimum temperature dropped lower than the turning point. However, for people living in the mast affluent areas, after the initial increase there was a decrease of mortality for colder days. Besides, when comparing the two spatiotemporal models (i.e. using nearby or central temperature monitoring station), while leaving the other predictors unchanged, this study showed that there was little difference in the overall model performances. Conclusion: This study indicated that the daily fluctuation of mortality was associated with daily temperature, while the spatial variation of mortality within this city could be explained by the geographical distribution of green space and socioeconomic factors. Since people living in affluent areas were found to he more tolerant of cold temperatures, it would be more efficient to tailor cold temperature health education and warning information for socioeconomically deprived communities.