Archives of Gerontology and Geriatrics 43 (2006) 85–91

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Life expectancy at the age of 65 years and environmental factors: An ecological study in Japan

Kazushi Okamoto*

Department of Epidemiology, Aichi Prefectural College of Nursing and Health, Togoku Kamishidami, Moriyama-ku, Nagoya 463-8502, Japan

Received 5 April 2005; received in revised form 7 September 2005; accepted 12 September 2005

Available online 10 November 2005

Abstract

The purpose of this study was to examine the factors associated with life expectancy at the age of 65 yearsusedastheindexoflongevity,usingpublisheddatainJapan.Lifeexpectancyattheageof65years wasobtainedfromthe19thlifetablein2000publishedbytheMinistryofHealth,LabourandWelfareof Japan. The associations between life expectancy at the age of 65 years and environmental factors were assessed by Spearman correlation coefficients. Life expectancy at the age of 65 years was higher in females (22.54 years) than in males (17.42 years). In this study, the number of public health nurses and leisuretimeperdaywerefoundsignificantlyassociatedwithlifeexpectancyattheageof65yearsinboth menandwomen.Formen,lifeexpectancyattheageof65yearswassignificantlyassociatedwithleisure time for sports and exercises and higher proportion of participation in volunteer activities in the community; for women, it was associated with a higher number of hospitals and proportion of participation in educational classes for the aged. Our ecological study might provide some clues to more practical planning for longevity in consideration of gender differences. # 2005 Elsevier Ireland Ltd. All rights reserved.

Keywords: Life expectancy; Ecological study; Geographical distribution; Longevity; Health care service

Introduction

Several countries (including Japan) have reported an increase in life expectancy. Many researchers have put efforts to identify the determinants of longevity such as socioeconomic status and lifestyle (Hatano, 1980; Okamoto et al., 1994; Lin et al., 2003). According to Lin et al. (2003), who examined the relationship between life expectancy and socioeconomic

* Tel.: 81 52 736 1401; fax: 81 52 736 1415. E-mail address: okamoto@aichi-nurs.ac.jp.

0167-4943/$ – see front matter # 2005 Elsevier Ireland Ltd. All rights reserved.

doi:10.1016/j.archger.2005.09.005

factors, longer expectancy was observed for individuals with higher levels of education and income, and for those who were married and employed in the USA. Cockerham (1997) also reportedthatpoorhealthlifestylesaremajorsocialdeterminantsoflifeexpectancyinRussia. With a few exceptions, most of these analytical studies have examined residents living in a specificareaandsmallnumberofsamples.Itispossiblethatlargeintra-individualvariability in the measurement of exposure will attenuate the associations. Ecological studies may be less subject to the effects of random error in the measurement of exposure. It is interesting to studytheecologicallifestyleandenvironmentalfactorsassociatedwithlongevityinJapan,as average life expectancy here is now the longest in the world. The uniformity of the data sources on demographic data and socioeconomic and environmental factors for all the geographical units within Japan is also advantageous.

According to Wingard (1984), two categories of lifestyle characteristics, i.e. social roles and behaviors are associated with male–female differences in health, and those factors may act synergistically on health. In Japan, women have a healthier lifestyle such as exercising more, smoking cigarettes less, and following healthier diets, compared with men. It is likely that there are gender differences in the factors associated with longevity. Very little is known about gender differences in the factors associated with longevity.

The aim of the research described here is to examine gender difference in the relationship between environmental factors such as socioeconomic, social and healthrelated behaviors and life expectancy at the age of 65 years, which is closely associated with longevity, using published statistics in Japan.

Methods

The figure of life expectancy of 65 years was obtained from the 19th life table published by the Ministry of Health, Labour and Welfare of Japan (2000). In this analysis, this table was used as an index for fluctuation of life expectancy at the age of 65 years by prefecture.

Environmental factors used to examine the relationship with life expectancy were as follows: yearly average air temperature, yearly sunshine hours, ratio of population 65 years old, ratio of employees in a primary industry, ratio of employees in a tertiary industry, benefits paid per actual beneficiary of national annuity, ratio of welfare expenditure for the aged, the number of public health nurses (person), general hospitals (per 100,000 persons), time spent per day at work, time spent per day in hobbies and amusements, time spent per day for sports, participation in community activities, and education classes for the aged.

The associations between life expectancy at the age of 65 years and environmental factors were assessed by Spearman correlation coefficients. All calculations were performed by SPSS Ver. 11.0 for Windows (Statistical Package for the Social Science, SPSS Inc., Chicago, Illinois).

Results

The national overall life expectancy of 65 years was higher in females (22.54 years) than in males (17.42 years) (Table 1). The relationship between the studied factors and life

Table 1

Distribution of ratio of life expectancy at the age of 65 years by sex