[Estimation of excess mortality associated with influenza epidemics specific for sex, age and cause of death in Japan during 1987-2005].
OBJECTIVE
The aim of this study is to clarify the excess mortality associated with influenza epidemics in Japan during the period from 1987 to 2005.


METHODS
Monthly data on the total number of deaths (excluding accidental deaths) and the numbers of deaths due to malignant neoplasms, heart disease, cerebrovascular disease, pneumonia, and renal failure were obtained from vital statistics from 1987-2005. The point estimates and range of excess mortality were evaluated using a model based on annual mortality and seasonal indices. Total mortality was analyzed for all ages, sex and for the following five age groups: 0-4, 5-24, 25-44, 45-64, and > or =65 yrs.


RESULTS
The excess number of deaths showed almost no difference in each influenza season between men and women. During each influenza season, approximately 85-90% of the excess mortality was attributed to the > or =65 yrs age group. During the 1995 and 1999 seasons, mortality increased significantly across all age groups. The highest point estimate of excess mortality in the > or =65 yrs age group was observed in 1999. From a comparison of the range of excess mortality in the > or =65 yrs age group by year, the excess mortality in 1995 appeared to be the highest of the examined years. The highest point estimate of excess mortality in the 0-4 yrs age group was observed in 1995. From a comparison of the range of excess mortality in the 0-4 yrs age group by year, the excess mortality in 1998 or 1999 appeared to be the highest of the examined years. Excess mortality in the 45-64 yrs and > or =65 yrs age groups showed an increasing tendency in the 1990s and a stabilizing tendency beginning in 2000. In addition, excess mortality during each epidemic was occurred in persons with pneumonia, heart disease, cerebrovascular disease, malignant neoplasms, and renal failure, accounting for approximately 20-50%, 20-40%, 20%, 5%, and 2% of all the excess mortality, respectively.


CONCLUSIONS
These results indicate that the majority of excess mortality occurred among the elderly and persons with pneumonia, heart disease, or cerebrovascular disease. Although it is unclear whether the increasing trend in the 1990s and the stabilizing trend beginning in 2000 were the result of vaccination measures, health measures for groups such as the elderly and heart disease patients are considered to be important for the future.
Takahashi
Mihoko
M
Division of Human and science, Faculty of Nursing, Yamanashi Prefectural University, 1-6-1 Ikeda, Kofu 400-0062, Japan. p_miho@yamanashi-ken.ac.jp
Nagai
Masaki
M
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002423:Cause of Death; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000401:mortality*; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012737:Sex Factors