Abstract
BackgroundThere is an extensive literature describing temperature-mortality associations in developed regions, but research from developing countries, and Africa in particular, is limited. MethodsWe conducted a time-series analysis using daily temperature data and a national dataset of all 8.8 million recorded deaths in South Africa between 1997 and 2013. Mortality and temperature data were linked at the district municipality level and relationships were estimated with a distributed lag non-linear model with 21 days of lag, and pooled in a multivariate meta-analysis. ResultsWe found an association between daily maximum temperature and mortality. The relative risk for all-age all-cause mortality on very cold and hot days (1st and 99th percentile of the temperature distribution) was 1.14 (1.10,1.17) and 1.06 (1.03,1.09), respectively, when compared to the minimum mortality temperature. This “U” shaped relationship was evident for every age and cause group investigated, except among 25–44 year olds. The strongest associations were in the youngest (< 5) and oldest (> 64) age groups and for cardiorespiratory causes. Heat effects occurred immediately after exposure but diminished quickly whereas cold effects were delayed but persistent. Overall, 3.4% of deaths (~ 290,000) in South Africa were attributable to non-optimum temperatures over the study period. We also present results for the 52 district municipalities individually. ConclusionsAn assessment of the largest-ever dataset for analyzing temperature-mortality associations in (South) Africa indicates mortality burdens associated with cold and heat, and identifies the young and elderly as particularly vulnerable.
Highlights
There is an extensive literature describing temperature-mortality associations in developed regions, but research from developing countries, and Africa in particular, is limited (Basu, 2009; Benmarhnia et al, 2015; Gasparrini et al, 2015b; Ryti et al, 2016)
The dataset was provided by Statistics South Africa, which estimates that death registration for adults is ~ 89% complete early in the study period, rising to ~ 94% by the end (Statistics South Africa, 2014a, 2014b)
We reduced the association in two dimensions: first to the overall temperature-mortality association, cumulating the risk over a 21-day lag period to account for the delayed effects of cold and for potential short-term mortality displacement; to the lagresponse associations corresponding to the 99th and 1st percentiles using the district-specific minimum mortality temperature (MMT) as a reference
Summary
There is an extensive literature describing temperature-mortality associations in developed regions, but research from developing countries, and Africa in particular, is limited (Basu, 2009; Benmarhnia et al, 2015; Gasparrini et al, 2015b; Ryti et al, 2016). Large segments of the population live in dwellings that do not adequately protect against heat and cold (Makaka and Meyer, 2006; Scovronick and Armstrong, 2012; United Nations Human Settlements Programme, 2011) All of these factors are known or putative modifiers of the effect of temperature on mortality (Basu, 2009; Benmarhnia et al, 2015; Ryti et al, 2016; Scovronick and Armstrong, 2012). The relative risk for allage all-cause mortality on very cold and hot days (1st and 99th percentile of the temperature distribution) was 1.14 (1.10,1.17) and 1.06 (1.03,1.09), respectively, when compared to the minimum mortality temperature This “U” shaped relationship was evident for every age and cause group investigated, except among 25–44 year olds. Conclusions: An assessment of the largest-ever dataset for analyzing temperature-mortality associations in (South) Africa indicates mortality burdens associated with cold and heat, and identifies the young and elderly as vulnerable
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