Space–Time Covariation of Mortality with Temperature: A Systematic Study of Deaths in France, 1968–2009

BACKGROUND: The temperature–mortality relationship has repeatedly been found, mostly in large cities, to be U/J-shaped, with higher minimum mortality temperature (MMT) at low latitudes being interpreted as indicating human adaptation to climate. OBJECTIVES: Our aim was to partition space with a high-resolution grid to assess the temperature–mortality relationship in a territory with wide climate diversity, over a period with notable climate warming. METHODS: The 16,487,668 death certificates of persons > 65 years of age who died of natural causes in continental France (1968–2009) were analyzed. A 30-km × 30-km grid was placed over the map of France. Generalized additive model regression was used to assess the temperature–mortality relationship for each grid square, and extract the MMT and the RM25 and RM25/18 (respectively, the ratios of mortality at 25°C/MMT and 25°C/18°C). Three periods were considered: 1968–1981 (P1), 1982–1995 (P2), and 1996–2009 (P3). RESULTS: All temperature–mortality curves computed over the 42-year period were U/J-shaped. MMT and mean summer temperature were strongly correlated. Mean MMT increased from 17.5°C for P1 to 17.8°C for P2 and to 18.2°C for P3 and paralleled the summer temperature increase observed between P1 and P3. The temporal MMT rise was below that expected from the geographic analysis. The RM25/18 ratio of mortality at 25°C versus that at 18°C declined significantly (p = 5 × 10(–5)) as warming increased: 18% for P1, 16% for P2, and 15% for P3. CONCLUSIONS: Results of this spatiotemporal analysis indicated some human adaptation to climate change, even in rural areas. CITATION: Todd N, Valleron AJ. 2015. Space–time covariation of mortality with temperature: a systematic study of deaths in France, 1968–2009. Environ Health Perspect 123:659–664; http://dx.doi.org/10.1289/ehp.1307771