Background: The effect of extreme temperature has become an increasing public health concern. Evaluating the impact of ambient temperature on morbidity has received less attention than its impact on mortality.
Methods: We performed a systematic literature review and extracted quantitative estimates of the effects of hot temperatures on cardiorespiratory morbidity. There were too few studies on effects of cold temperatures to warrant a summary. Pooled estimates of effects of heat were calculated using a Bayesian hierarchical approach that allowed multiple results to be included from the same study, particularly results at different latitudes and with varying lagged effects.
Results: Twenty-one studies were included in the final meta-analysis. The pooled results suggest an increase of 3.2% (95% posterior interval = −3.2% to 10.1%) in respiratory morbidity with 1°C increase on hot days. No apparent association was observed for cardiovascular morbidity (−0.5% [−3.0% to 2.1%]). The length of lags had inconsistent effects on the risk of respiratory and cardiovascular morbidity, whereas latitude had little effect on either.
Conclusions: The effects of temperature on cardiorespiratory morbidity seemed to be smaller and more variable than previous findings related to mortality.
From the aSchool of Public Health and Social Work, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia; bSchool of Environment, Griffith University, Brisbane, Australia; and cSchool of Public Health, Anhui Medical University, Hefei, Anhui, China.
Submitted 29 June 2011; accepted 7 February 2012; posted 23 April 2012.
Supported partly by funds from the Australian Research Council (DP1095752) (to S.T. and D.C.); and by NHMRC Research Fellowship (#553043) (to S.T.). The authors reported no other financial interests related to this research.
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Correspondence: Shilu Tong, School of Public Health and Social Work, Institute of Health and Biomedical Innovation, Queensland University of Technology, Victoria Park Road, Kelvin Grove, QLD 4059, Australia. E-mail: firstname.lastname@example.org.