Comparative analysis of daily and hourly temperature variability in association with all-cause and cardiorespiratory mortality in 45 US cities

Abstract

BackgroundTemperature variability (TV) has been widely associated with increased mortality risk and burden.Extensive researches have used the standard deviations of several days' daily maximum and minimum temperatures or hourly mean temperatures as daily and hourly TV measures (TV daily and TV hourly ).However, comparative analysis of daily and hourly TV related to cardiorespiratory mortality is still limited. MethodsWe collected daily mortality and meteorological data in 45 US metropolises, 1987-2000. A three-stage analyses were adopted to investigate TV-mortality associations using TV daily and TV hourly as exposure metrics. We rst applied a time-series quasi-Poisson regression to estimate location-speci c TV-mortality relationship, which were then pooled using random-effects meta-analysis with maximum likelihood estimation (MLE). We additionally calculated attributable fractions as a re ection of total mortality burden associated with TV. Strati ed analyses by age were also performed to identify the susceptible group to TV-related risk. ResultsThere were a total of 15.4 million all-cause deaths, of which 6.1 million were from cardiovascular and 1.2 million were from respiratory causes. Per 1 °C increase in TV daily and TV hourly was associated with an increase of 0.53% (95% con dence interval: 0.31-0.76%) and 0.52% (0.26-0.79%) in cardiovascular mortality risks, 0.62% (0.26-0.98%) and 0.53% (0.13-0.94%) in respiratory mortality risks. Estimations of cardiovascular attributable fractions for TV daily and TV hourly were 2.43% (1.42-3.43%) vs 1.63% (0.82-2.43%), whereas respiratory attributable fractions were 3.07% (1.11-4.99%) vs 1.89% (0.43-3.34%). Both daily and hourly indexes showed approximately linear relationships with different mortality categories and similar lag patterns, but greater fractions were estimated using TV daily than those using TV hourly .People over 75 years old were relatively more vulnerable to TV-induced risks of mortality. ConclusionsBoth TV daily and TV hourly signi cantly increased all-cause and cardiorespiratory mortality risks and burden. Daily TV metrics resembled hourly in risk effects, whilst greater mortality burden was found in TV daily than TV hourly . Our ndings may add signi cance to TV-mortality research and help to promote optimal health management strategies to better mitigate TV-related health effect.