The narrowing sex differential in life expectancy in high-income populations: effects of differences in the age pattern of mortality

The changing gender differences in life expectancy in Korea 1970-2005

Women live much longer than men in Korea, with remarkable gains in life expectancy at birth for the past decades. The gender differential has steadily increased over time, reaching a peak of more than 8 years in 1980s, and decreased thereafter to 6.7 years in 2005. Studies to investigate the pattern and contributing factors to changes in the life expectancy gender gap have been mostly from Western countries, and there has been no such study in Asian countries, except in Japan. We therefore aimed to examine age- and cause-specific contributions to the changing gender differentials in life expectancy in Korea, in particular the decline of the gap, using a decomposition method. Between 1970 and 1979 when the gender gap in life expectancy widened, faster mortality decline among women in ages 20-44 explained 66% of the total increase in the gender gap, which would be due to substantial improvements in reproductive health among women and excess male mortality in occupational injuries and transport accidents. Although greater survival advantage among elderly women over 70 contributed to further increase in the gender gap, the contributions from younger ages with the ages 15-64 contributing the most (-2 years) resulted in the overall reduction of the gender gap which began in 1992 and continued to 2005. Among causes of death, liver diseases (-0.5 years, 38% of the total decline), transport accidents (-0.4 years, 31%), hypertensive diseases (-0.3 years, 19%), stroke (-0.1 years, 11%), and tuberculosis (-0.1 years) contributed the most to the overall 1.4 years reduction in the gender gap. However, changes in mortality from lung cancer (+0.3 years), suicide (+0.3 years), chronic lower respiratory diseases (+0.2 years), and ischemic heart diseases (+0.1 years) contributed to widening the gap during the same period. In sum, while smoking-related causes of death have contributed most to the narrowing gap in most other industrialized countries, these causes contributed toward increasing the gender gap in Korea. Instead, liver disease, hypertension-related diseases, and transport accidents were major contributing causes of death to the narrowing of gender differentials in life expectancy in Korea.

Gender gaps in life expectancy: generalized trends and negative associations with development indices in OECD countries

BACKGROUND

Life expectancy (LE) is a major marker of individual survival. It also serves as a guide to highlight both the progress and the gaps in total social and societal health. Comparative LE in concert with measures of gender-specific experience, indices of empowerment and societal happiness and development offer a comparative tool to examine trends and similarities of societal progress as seen through the lens of cross-national experience.

METHODS

To determine the gender gaps in LE (GGLE) trends, we performed a longitudinal analysis, covering a period of 49 years (1960-2008). To examine the association of GGLE with development indices, we used the 2007 GGLE data, the newest happiness data mostly drawn from 2006; the 2006 Human Development Index (HDI) data and the 2006 Gender Empowerment Measure (GEM) data.

RESULTS

It revealed that most of the Organization for Economic Co-operation and Development (OECD) countries had a GGLE trend that occurred in an inverted U-curve fashion. We divided them into three subgroups based on the peak years of respective GGLE. The earlier the peak year, the happier the countries, the higher the HDI and the smaller the current GGLE are. Association analysis indicates that Happiness, HDI and GEM are all negatively associated with GGLE.

CONCLUSION

This pattern suggests that GGLE undergoes three phases of growth, peak and stability and decline. Japan will soon be seeing its GGLE gradually shrinking in the foreseeable future. The continuing increases in Happiness, HDI and GEM are associated with a decrease in GGLE, which should be carefully taken into consideration.

Dietary effects on sex-specific health dynamics of medfly: support for the dynamic equilibrium model of aging

We examined experimentally the relationship between the period of unhealthy life and longevity in the medfly by using the first sign of supine behavior (upside down; immobile) in medflies as an indication of their poor health and by altering cohort longevity through dietary manipulations. Our main findings included the following: i) for longer lived medflies it was more likely to observe the supine behavior while shorter lived flies would more likely die before exhibiting the supine behavior. ii) males have similar total life expectancy as females but a longer healthy life expectancy; iii) the total number of healthy days, spent in the pre-supine period, and the amount of healthy life span as a fraction of the total lifespan varied with both sex and diet; iv) despite the large difference in longevity between both male and female medflies when reared on sugar-only diets versus on full diets, the differences in the fraction of their lifespans in the disabled state were relatively modest (64 vs 61% in females and 77 vs 72% in males). This finding that there is no significant change in the proportion of the life course in the unhealthy state is consistent with the 'dynamic equilibrium' model of healthy aging.

Variance in Death and Its Implications for Modeling and Forecasting Mortality

The slope and curvature of the survivorship function reflect the considerable amount of variance in length of life found in any human population. Part is due to the well-known variation in life expectancy between groups: large differences according to race, sex, socioeconomic status, or other covariates. But within-group variance is large even in narrowly defined groups, and changes substantially and inversely with the group average length of life. We show that variance in length of life is inversely related to the Gompertz slope of log mortality through age, and we reveal its relationship to variance in a multiplicative frailty index. Our findings bear a variety of implications for modeling and forecasting mortality. In particular, we examine how the assumption of proportional hazards fails to account adequately for differences in subgroup variance, and we discuss how several common forecasting models treat the variance along the temporal dimension.

SEX DIFFERENCES IN LIFE EXPECTANCY IN CANADA: IMMIGRANT AND NATIVE-BORN POPULATIONS

A growing body of research often indicates that immigrant populations in Western countries enjoy a lower level of mortality in relation to their native-born host populations. In this literature, sex differences in mortality are often reported but substantive analyses of the differences are generally lacking. The present investigation looks at sex differences in life expectancy with specific reference to immigrant and Canadian-born populations in Canada during 1971 and 2001. For these two populations, sex differences in expectation of life at birth are decomposed into cause-of-death components. Immigrants in Canada have a higher life expectancy than their Canadian-born counterparts. In absolute terms, immigrant females enjoy the highest life expectancy. Inrelativeterms, however, immigrant men show a larger longevity advantage, as their expectation of life at birth exceeds that of Canadian-born men by a wider margin than do foreign-born females in relation to Canadian-born females. It is also found that immigrants have a smaller sex differential in life expectancy as compared with the Canadian born. Decomposition analysis shows this is a function of immigrants having smaller sex differences in death rates from heart disease and cancer. Factors thought to underlie these differentials between immigrants and the Canadian born are discussed and suggestions for further research are given.

Gender gap in health expectancy

Men have higher death rates than women, but women do worse with regard to physical strength, disability, and other health outcomes, the so called male-female health-survival paradox. The paradox is likely to be due to multiple causes that include biological, behavioral, and social differences between the sexes. Despite decades of research on the male-female health-survival paradox, we still do not fully recognize whether behavioral factors explain most of the gender gap or whether biological and social differences contribute more substantially to the explanation of the sex differences in health and mortality. Little work has been done to investigate the magnitude of sex differences in healthy life expectancy and unhealthy life expectancy, as well as to examine the contribution of mortality and disability levels to the sex gap in health expectancy. The five selected works presented at the Réseau Espérance de Vie en Santé (REVES) Meeting 2009 in Copenhagen, and published in this issue, provide new insights into sex differences in health expectancy. The papers examine sex differences in health expectancy indicators in the EU countries, as well as trends in health expectancy in Hong Kong and in the US. They go beyond description of sex differences in health expectancy and assess the contributions of mortality and disability to gender differences in healthy life years and unhealthy life years, investigate temporal changes in sex differential health expectancy, as well as analyze contributions of time and age dimensions to the gender gap. They also show that there is still work to be done to indentify and quantify mechanisms underlying sex differences in longevity, health, and aging.

Cross-national comparison of sex differences in health and mortality in Denmark, Japan and the US

The present study aims to compare the direction and magnitude of sex differences in mortality and major health dimensions across Denmark, Japan and the US. The Human Mortality Database was used to examine sex differences in age-specific mortality rates. The Danish twin surveys, the Danish 1905-Cohort Study, the Health and Retirement Study, and the Nihon University Japanese Longitudinal Study of Aging were used to examine sex differences in health. Men had consistently higher mortality rates at all ages in all three countries, but they also had a substantial advantage in handgrip strength compared with the same-aged women. Sex differences in activities of daily living (ADL) became pronounced among individuals aged 85+ in all three countries. Depression levels tended to be higher in women, particularly, in Denmark and the HRS, and only small sex differences were observed in the immediate recall test and Mini-Mental State Exam. The present study revealed consistent sex differentials in survival and physical health, self-rated health and cognition at older ages, whereas the pattern of sex differences in depressive symptoms was country-specific.

Cross-national comparison of sex differences in health and mortality in Denmark, Japan and the US

The present study aims to compare the direction and magnitude of sex differences in mortality and major health dimensions across Denmark, Japan and the US. The Human Mortality Database was used to examine sex differences in age-specific mortality rates. The Danish twin surveys, the Danish 1905-Cohort Study, the Health and Retirement Study, and the Nihon University Japanese Longitudinal Study of Aging were used to examine sex differences in health. Men had consistently higher mortality rates at all ages in all three countries, but they also had a substantial advantage in handgrip strength compared with the same-aged women. Sex differences in activities of daily living (ADL) became pronounced among individuals aged 85+ in all three countries. Depression levels tended to be higher in women, particularly, in Denmark and the HRS, and only small sex differences were observed in the immediate recall test and Mini-Mental State Exam. The present study revealed consistent sex differentials in survival and physical health, self-rated health and cognition at older ages, whereas the pattern of sex differences in depressive symptoms was country-specific.

Improving mortality prediction using biosocial surveys

The authors used data from a nationally representative survey of 933 adults aged 54 years or older (mean age = 66.2 years; standard deviation, 8.0) in Taiwan to explore whether mortality prediction at older ages is improved by the use of 3 clusters of biomarkers: 1) standard cardiovascular and metabolic risk factors; 2) markers of disease progression; and 3) nonclinical (neuroendocrine and immune) markers. They also evaluated the extent to which these biomarkers account for the female advantage in survival. Estimates from logistic regression models of the probability of dying between 2000 and 2006 (162 deaths; mean length of follow-up = 5.8 years) showed that inclusion of each of the 3 sets of markers significantly (P = 0.024, P = 0.002, and P = 0.003, respectively) improved discriminatory power in comparison with a base model that adjusted for demographic characteristics, smoking, and baseline health status. The set of disease progression markers and the set of nonclinical markers each provided more discriminatory power than standard risk factors. Most of the excess male mortality resulted from the men being more likely than women to smoke, but each of 3 markers related to disease progression or inflammation (albumin, neutrophils, and interleukin-6) explained more than 10% of excess male mortality.

A decomposition method based on a model of continuous change

A demographic measure is often expressed as a deterministic or stochastic function of multiple variables (covariates), and a general problem (the decomposition problem) is to assess contributions of individual covariates to a difference in the demographic measure (dependent variable) between two populations. We propose a method of decomposition analysis based on an assumption that covariates change continuously along an actual or hypothetical dimension. This assumption leads to a general model that logically justifies the additivity of covariate effects and the elimination of interaction terms, even if the dependent variable itself is a nonadditive function. A comparison with earlier methods illustrates other practical advantages of the method: in addition to an absence of residuals or interaction terms, the method can easily handle a large number of covariates and does not require a logically meaningful ordering of covariates. Two empirical examples show that the method can be applied flexibly to a wide variety of decomposition problems. This study also suggests that when data are available at multiple time points over a long interval, it is more accurate to compute an aggregated decomposition based on multiple subintervals than to compute a single decomposition for the entire study period.

Gender differences in daily smoking prevalence in different age strata: a population-based study in southern Sweden

OBJECTIVES

To investigate gender differences in daily smoking prevalence in different age groups in southern Sweden.

METHODS

The 2004 public-health survey in Skane is a cross-sectional study. A total of 27,757 persons aged 18-80 years answered a postal questionnaire, which represents 59% of the random sample. A logistic regression model was used to investigate the associations between gender and daily smoking according to age. The multivariate analysis was performed to investigate the importance of possible confounders (country of origin, education, snus use, alcohol consumption, leisure-time physical activity, and BMI) on the gender differences in daily smoking in different age groups.

RESULTS

14.9% of the men and 18.1% of the women were daily smokers. Middle-aged respondents were daily smokers to a significantly higher extent than young and old respondents. The prevalence of daily smoking also varied according to other demographic, socioeconomic, health related behaviour, and BMI characteristics. The crude odds ratios of daily smoking were 1.79 (1.42-2.26) among women compared to men in the 18-24 years age group, and 0.95 (0.80-1.12) in the 65-80 years age group. These odds ratios changed to 2.00 (1.49-2.67) and 0.95 (0.76-1.18), respectively, when all confounders were included.

CONCLUSIONS

For the first time in Sweden women have a higher prevalence of daily smoking than men. The odds ratios of daily smoking are highest among women compared to men in the youngest age group of 18-24 years and the odds ratios decrease with increasing age. The findings point to a serious public health problem. Strategic interventions targeting young women's tobacco smoking are needed.

Longevity disparities in multiethnic Hawaii: an analysis of 2000 life tables

OBJECTIVE

We examined differences among seven major ethnic groups in Hawaii in life expectancy at birth (e[0]) and mortality at broad age groups.

METHODS

We constructed life tables for 2000 for Caucasian, Chinese, Filipino, Hawaiian, Japanese, Korean, and Samoan ethnic groups in Hawaii. We partitioned overall mortality into broad age groups: <15 (representing premature mortality), 15-65 (representing working age), and 66-84 and > or =85 (representing senescent mortality).

RESULTS

The overall e(O) in Hawaii was 80.5 years, but the difference between the longest-living group (Chinese) and the shortest-living group (Samoan) was 13 years. Chinese had the lowest mortality rates in each age group except the > or =85 category. In this last age group, we observed anomalously low rates for some new immigrant groups (especially Samoan males) suggesting, as a cause, that elders in these immigrant groups may return to natal countries in their old age and die there. In the <15 age group, mortality rates for Samoans and Koreans were highest, especially for Korean girls, suggesting some continuance in the U.S. of a preference for boy children. Outside of these anomalies, ethnic differences in e(O) were likely explained by socioeconomic and behavioral variables known to affect mortality levels, which are closely associated with ethnicity in Hawaii.

CONCLUSIONS

These findings confirm the need to disaggregate Asian and Pacific Islander data, to conduct ethnic-specific research, and to address socioeconomic disparities.

The Penna Model of Biological Aging

This review deals with computer simulation of biological aging, particularly with the Penna model of 1995. They are based on the mutation accumulation theory of half a century ago. The results agree well with demographical reality, and also with the seemingly contradictory influence of predators on the aging of prey.