Modification by influenza on health effects of air pollution in Hong Kong.
BACKGROUND
Both influenza viruses and air pollutants have been well documented as major hazards to human health, but few epidemiologic studies have assessed effect modification of influenza on health effects of ambient air pollutants.


OBJECTIVE
We aimed to assess modifying effects of influenza on health effects of ambient air pollutants.


METHODS
We applied Poisson regression to daily numbers of hospitalizations and mortality to develop core models after adjustment for potential time-varying confounding variables. We assessed modification of influenza by adding variables for concentrations of single ambient air pollutants and proportions of influenza-positive specimens (influenza intensity) and their cross-product terms.


RESULTS
We found significant effect modification of influenza (p < 0.05) for effects of ozone. When influenza intensity is assumed to increase from 0% to 10%, the excess risks per 10-microg/m(3) increase in concentration of O(3) increased 0.24% and 0.40% for hospitalization of respiratory disease in the all-ages group and >or= 65 year age group, respectively; 0.46% for hospitalization of acute respiratory disease in the all-ages group; and 0.40% for hospitalization of chronic obstructive pulmonary disease in the >or= 65 group. The estimated increases in the excess risks for mortality of respiratory disease and chronic obstructive pulmonary disease in the all-ages group were 0.59% and 1.05%, respectively. We found no significant modification of influenza on effects of other pollutants in most disease outcomes under study.


CONCLUSIONS
Influenza activity could be an effect modifier for the health effects of air pollutants particularly for O(3) and should be considered in the studies for short-term effects of air pollutants on health.
Wong
Chit Ming
CM
Department of Community Medicine and School of Public Health, University of Hong Kong, Hong Kong Special Administration Region, People's Republic of China.
Yang
Lin
L
Thach
Thuan Quoc
TQ
Chau
Patsy Yuen Kwan
PY
Chan
King Pan
KP
Thomas
G Neil
GN
Lam
Tai Hing
TH
Wong
Tze Wai
TW
Hedley
Anthony J
AJ
Peiris
J S Malik
JS
D000293:Adolescent; D000328:Adult; D000368:Aged; D000397:Air Pollution / Q000009:adverse effects*; D002318:Cardiovascular Diseases / Q000401:mortality; D002648:Child; D002675:Child, Preschool; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010126:Ozone / Q000633:toxicity; D012044:Regression Analysis; D012120:Respiration Disorders / Q000401:mortality; D012307:Risk Factors; D055815:Young Adult
D010126:Ozone