High temperatures-related elderly mortality varied greatly from year to year: important information for heat-warning systems

Abstract

We examined the variation in association between high temperatures and elderly mortality (age ≥ 75 years) from year to year in 83 US cities between 1987 and 2000. We used a Poisson regression model and decomposed the mortality risk for high temperatures into: a “main effect” due to high temperatures using lagged non-linear function, and an “added effect” due to consecutive high temperature days. We pooled yearly effects across both regional and national levels. The high temperature effects (both main and added effects) on elderly mortality varied greatly from year to year. In every city there was at least one year where higher temperatures were associated with lower mortality. Years with relatively high heat-related mortality were often followed by years with relatively low mortality. These year to year changes have important consequences for heat-warning systems and for predictions of heat-related mortality due to climate change.

Exploring the effects of high temperature on mortality in four cities in the Philippines using various heat wave definitions in different mortality subgroups

“…Other studies have observed higher risks among the elderly due to the decreased thermoregulatory capacity when a person ages [20,29]. Factors such as dehydration affect the elderly through decreased sweat production and reduced direct loss of skin warmth, thereby decreasing the thermoregulation and thermal homeostasis [30,31]. Although the elderly people have greater effects estimates compared to the other age-specific risk groups, as seen in Table 5, the estimates were not significant.…”

Geographic Dimensions of Heat-Related Mortality in Seven United States Cities

“…New knowledge about the human response to heat could lead to more efficient allocation of resources associated with the activation of heat emergency management protocols as well as those associated with longer-term mitigation and adaptation strategies. Recent research has contributed to increased awareness of geographic variability in the response to heat within large metropolitan areas (e.g., Vaneckova et al 2010 and of intra-annual variability in the metropolitan aggregate-scale response to heat (e.g., Guo et al 2012). But little effort has been directed at the intersection of these sources of variability-exploring how the intra-city human response to heat, in particular morbidity and mortality, changes from one year to another.…”

“…It is known that the heat-mortality response varies across time (e.g., , Rocklov et al 2009, Guo et al 2012. Although considerable debate continues regarding future climate change and population adaptation, the increase in temperatures in recent years combined with urban heat island impacts has resulted in individuals being more frequently exposed to thermally stressful conditions in some locations (Arnfield et al 2002, Wilby et al 2003.…”

“…The human response to high heat and humidity varies from individual to individual, but over large populations there is clear evidence that extreme summertime conditions lead to elevated mortality and morbidity rates , Guo et al 2012). This information has contributed to the adoption of a number of measures aimed at protecting public health when dangerous conditions are forecast, including heat-health watch-warning systems (Hondula et al 2013b).…”

“…We identified an absolute temperature threshold (i.e., one that does not vary across months or years), but research efforts continue be directed to improve the identification and definition of high-risk extreme heat days (e.g., Barnett et al 2012, Zhang et al 2012, Antics et al 2013). There may be both theoretical and model performance advantages to using more complex metrics for quantifying the relationship between human health and heat, and the optimal metric could vary from one city to another.…”