Comparison of patterns in influenza-associated excess mortality among men and women in Hong Kong

Abstract

BACKGROUND: The burden of mortality attributable to influenza virus can be quantified by influenza-associated excess deaths estimated from statistical models. Given the discrepancies that have often been observed in the prevalence and burden of major diseases between men and women, we aimed to examine the patterns in influenza-associated excess mortality among men and women in Hong Kong in the past decade. MATERIALS AND METHODS: Multiple linear regression models were applied to age-specific all-cause and cause-specific mortality rates in Hong Kong from 1998 through 2009 for men and women separately. The activities of different types/subtypes of influenza virus and co-circulating respiratory syncytial virus were adjusted as the product of influenza-like illness rates from sentinel surveillance and laboratory detection rates of the specific viruses. Models were also adjusted for environmental temperature and absolute humidity and periodic temporal trends in mortality rates. The influenza-associated excess mortality was measured as the differences between estimated mortality rates in the presence or absence of influenza activity. Attributable fractions were estimated for each cause. RESULTS: The annual influenza-associated all-cause excess mortality rates were 9.6 and 12.6 per 100,000 person-years for men and women from 1998 through 2009. The attributable fractions of all-cause deaths were 2.0% and 2.1% in men and women, respectively. More than 90% of the influenza-associated all-cause excess deaths were estimated in the elderly for both men and women. Cardiorespiratory diseases accounted for more influenza-associated excess deaths in men (80%) than in women (70%). CONCLUSIONS: Influenza infection led to a higher number of excess deaths among men than women each year in Hong Kong, but more men die of all causes and the attributable fractions were very similar for men and women. Most of the influenza-associated excess deaths occurred in the elderly for both sexes. Cardiorespiratory diseases accounted for the majority of the influenza-associated excess deaths in both sexes, particularly among men.