title: Mortality related to cold and heat. What do we learn from dairy cattle?
abstract: Extreme temperatures are associated with increased mortality among humans. Because similar epidemiologic studies in animals may add to the existing evidence, we investigated the association between ambient temperature and the risk of mortality among dairy cattle. We used data on 87,108 dairy cow deaths in Belgium from 2006 to 2009, and we combined a case-crossover design with distributed lag non-linear models. Province-specific results were combined in a multivariate meta-analysis. Relative to the estimated minimum mortality temperature of 15.4°C (75th percentile), the pooled cumulative relative risks over lag 0-25 days were 1.26 (95% CI: 1.11, 1.42) for extreme cold (1st percentile, -3.5°C), 1.35 (95% CI: 1.19, 1.54) for moderate cold (5th percentile, -0.3°C), 1.09 (95% CI: 1.02, 1.17) for moderate heat (95th percentile, 19.7°C), and 1.26 (95% CI: 1.08; 1.48) for extreme heat (99th percentile, 22.6°C). The temporal pattern of the temperature-mortality association was similar to that observed in humans, i.e. acute effects of heat and delayed and prolonged effects of cold. Seasonal analyses suggested that most of the temperature-related mortality, including cold effects, occurred in the warm season. Our study reinforces the evidence on the plausibility of causal effects in humans.
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: Bianca
authors.initials: B
authors.lastname: Cox
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene & Tropical Medicine (LSHTM), London, UK; Department of Medical Statistics, LSHTM, London, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gasparrini
authors.affiliation: Public Health and Surveillance, Scientific Institute of Public Health (WIV-ISP), Brussels, Belgium.
authors.forename: Boudewijn
authors.initials: B
authors.lastname: Catry
authors.affiliation: Royal Meteorological Institute, Brussels, Belgium.
authors.forename: Andy
authors.initials: A
authors.lastname: Delcloo
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: Esmée
authors.initials: E
authors.lastname: Bijnens
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium.
authors.forename: Jaco
authors.initials: J
authors.lastname: Vangronsveld
authors.affiliation: Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium; Department of Public Health and Primary Care, Leuven University, Leuven, Belgium. Electronic address: tim.nawrot@uhasselt.be.
authors.forename: Tim S
authors.initials: TS
authors.lastname: Nawrot
mesh_terms: D000818:Animals; D001530:Belgium; D002417:Cattle / Q000502:physiology*; D003080:Cold Temperature / Q000009:adverse effects*; D018592:Cross-Over Studies; D003612:Dairying; D055873:Extreme Cold / Q000009:adverse effects; D055874:Extreme Heat / Q000009:adverse effects; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D015999:Multivariate Analysis; D017711:Nonlinear Dynamics; D012621:Seasons
keywords: Cold; DLNM; Dairy cattle; Heat; Mortality