Effect modification in the temperature extremes by mortality subgroups among the tropical cities of the Philippines

Temperature-mortality relationships have been extensively probed with varying temperature range but with relatively similar patterns and in some instances are being modified by specific mortality groups such as causes of mortality, sex, and age.

This study aimed to determine the risk attributions in the extreme temperatures and also identified the risks associated with the various mortality subgroups.

We used the 2006-2010 daily average meteorological and daily mortality variables from the Philippine Atmospheric Geophysical and Astronomical Services Administration and Philippine Statistics Authority-National Statistics Office, respectively. Mortality data were divided according to cause (cardiovascular and respiratory), sex, and age (0-14 years, 15-64 years, and >64 years). We performed a two-stage analysis to estimate the extreme temperature effects stratified by the different mortality subgroups to observe the effect modification.

In the pooled analysis, greater risks were observed in the extreme high temperature (99th temperature percentile; RR (relative risk)=2.48 CI: 1.55-3.98) compared to the extreme low temperature (1st temperature percentile; RR=1.23 CI: 0.88-1.72). Furthermore, effect modification by mortality subgroups was evident, especially higher risks for extreme temperatures with respiratory-related diseases, women, and elderly.

Both sex and age were found to effect modify the risks in extreme temperatures of tropical cities; hence, health-related policies should take these risk variations into consideration to create strategies with respect to the risk population.