Assessment of the effect of cold and hot temperatures on mortality in Ontario, Canada: a population-based study.
BACKGROUND
Ambient high temperature is associated with death; however, heat-related risk of death has not been quantified systematically in Ontario, the most populous province in Canada. Less is known about cold-related risk in this population. Our objective was to quantify the health impact from cold and hot temperatures in Ontario.


METHODS
The study population consisted of all residents of Ontario who died between Jan. 1, 1996, and Dec. 31, 2010, from any nonaccidental cause. A case-crossover analysis was applied to assess the relation between daily temperature fluctuation and deaths from nonaccidental and selected causes in cold (December-February) and warm (June-August) seasons, respectively, adjusting for various potential confounders. Risk estimates were obtained for each census division, then pooled across Ontario. We examined potential effect modification for selected comorbidities and sociodemographic characteristics.


RESULTS
In warm seasons, each 5°C increase in daily mean temperature was associated with a 2.5% increase in nonaccidental deaths (95% confidence interval [CI] = 1.3% to 3.8%) on the day of exposure (lag 0). In cold seasons, each 5°C decrease in daily temperature was associated with a 3.0% (95% CI 1.8% to 4.2%) increase in nonaccidental deaths, which persisted over 7 days (lag 0-6). The cold-related effects (lag 0-6) were stronger for cardiovascular-related deaths (any cardiovascular death: 4.1%, 95% CI 2.3% to 5.9%; ischemic heart disease: 5.8%, 95% CI 3.6% to 8.1%), especially among people less than 65 years of age (8.0%, 95% CI 3.0% to 13.0%). Conversely, heat most strongly increased respiratory-related deaths during admission to hospital (26.0%, 95% CI 0% to 61.4%). Across Ontario, each 5°C change in daily temperature was estimated to induce 7 excess deaths per day in cold seasons and 4 excess deaths in warm seasons.


CONCLUSIONS
Heat contributed to excess deaths in Ontario, although the effect of cold weather appeared to be greater. Further work is required to better define high-risk subgroups, which might include the homeless and people with inadequately heated housing.
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Hong
H
Chen
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Jun
J
Wang
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Qiongsi
Q
Li
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Abderrahmane
A
Yagouti
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Eric
E
Lavigne
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Richard
R
Foty
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Richard T
RT
Burnett
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Paul J
PJ
Villeneuve
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Sabit
S
Cakmak
Public Health Ontario (Chen, Wang, Li, Copes); Dalla Lana School of Public Health (Chen, Foty, Villeneuve, Copes), University of Toronto, Toronto, Ont.; Institute for Clinical Evaluative Sciences (Chen), Toronto, Ont.; Climate Change and Health Office (Yagouti), Health Canada; Air Health Science Division (Lavigne), Health Canada; Department of Epidemiology and Community Medicine (Lavigne), University of Ottawa, Ottawa, Ont.; Sick Kids Hospital (Foty), Toronto, Ont.; Population Studies Division (Burnett, Cakmak), Health Canada; Department of Health Sciences (Villeneuve), Carleton University, Ottawa, Ont.
Ray
R
Copes