Ambient temperature, seasonal influenza and risk of cardiovascular disease in a subtropical area in Southern China

Kirran N Mohammad; Emily Ying Yang Chan; Martin Chi Sang Wong; William Bernard Goggins; Ka Chun Chong

doi:10.1016/j.envres.2020.109546

Ambient temperature, seasonal influenza and risk of cardiovascular disease in a subtropical area in Southern China

Environ Res. 2020 Jul:186:109546. doi: 10.1016/j.envres.2020.109546. Epub 2020 Apr 18.

Authors

Kirran N Mohammad¹, Emily Ying Yang Chan¹, Martin Chi Sang Wong¹, William Bernard Goggins¹, Ka Chun Chong²

Affiliations

¹ School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China.
² School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China; Clinical Trials and Biostatistics Laboratory, Shenzhen Research Institute, The Chinese University of Hong Kong, China; Centre for Health System and Policy Research, The Chinese University of Hong Kong, Hong Kong, China. Electronic address: marc@cuhk.edu.hk.

PMID: 32334173
DOI: 10.1016/j.envres.2020.109546

Abstract

Background: Given the regular winter recurrence of influenza epidemics and the biologically plausible association between seasonal influenza and cardiovascular events, researchers assumed a valid and reliable influenza forecast could envision the timing and burden of winter surge in cardiovascular (CVD) hospitalizations. This, however, is well justified only in temperate regions. In this study, we aim to investigate the temporal association between ambient temperature, seasonal influenza and risk of cardiovascular events in a subtropical city.

Methods: Generalized additive model was used in conjunction with distributed-lag non-linear model of quasi-Poisson family to estimate the association of interest with daily CVD admissions as outcome and daily influenza admissions as predictor, while controlling for meteorological factors (i.e. temperature, relative humidity, wind speed and total rainfall) and respiratory pollutants (i.e. nitrogen dioxide, sulphur dioxide, ozone and PM₁₀). Results were expressed in the form of relative risk (RR).

Results: Using median as the reference value, a U-shaped association was observed between CVD admissions and temperature. A slight decrease in RR was detected mainly towards the lower end of the temperature scale after adjusting for influenza admissions. Risk of CVD admission was found to be positively associated with the number of influenza hospitalization cases; this association remained consistent and statistically significant across subgroups of age except for those aged 5-49 years.

Conclusion: The slight reduction in CVD admission risk towards the lower end of the temperature scale after controlling for influenza activity might be attributed to the winter peaks of influenza, meaning that the effect of low temperature on CVD admissions might be partly mediated by influenza infection. In summary, this study reassures us that ambient temperature is independently associated with CVD hospital admissions and offers support for a positive association between seasonal influenza activity and cardiovascular events in Hong Kong.

Keywords: Cardiovascular disease; Distributed-lag non-linear model; Seasonal influenza; Subtropics; Temperature.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adolescent
Adult
Air Pollutants* / analysis
Air Pollution* / analysis
Cardiovascular Diseases* / epidemiology
Child
Child, Preschool
China / epidemiology
Hong Kong
Hospitalization
Humans
Influenza, Human* / epidemiology
Middle Aged
Seasons
Temperature
Young Adult

Substances

Air Pollutants