Anna Oksuzyan

Men: good health and high mortality. Sex differences in health and aging.

This review examines sex differences in health and survival, with a focus on the Nordic countries. There is a remarkable discrepancy between the health and survival of the sexes: men are physically stronger and have fewer disabilities, but have substantially higher mortality at all ages compared with women: the so-called male-female health-survival paradox. A number of proposed explanations for this paradox are rooted in biological, social, and psychological interpretations. It is likely to be due to multiple causes that include fundamental biological differences between the sexes such as genetic factors, immune system responses, hormones, and disease patterns. Behavioral differences such as risk-taking and reluctance to seek and comply with medical treatment may also play a role. Another consideration is that part of the difference may be due to methodological challenges, such as selective non-participation and under-reporting of health problems, and delayed seeking of treatment by men. The Nordic countries provide a unique opportunity for such studies, as they have good-quality data in their national health registers, which cover the whole population, and a long tradition of high participation rates in surveys.

Physical and cognitive functioning of people older than 90 years: a comparison of two Danish cohorts born 10 years apart

BACKGROUND A rapidly increasing proportion of people in high-income countries are surviving into their tenth decade. Concern is widespread that the basis for this development is the survival of frail and disabled elderly people into very old age. To investigate this issue, we compared the cognitive and physical functioning of two cohorts of Danish nonagenarians, born 10 years apart. METHODS People in the first cohort were born in 1905 and assessed at age 93 years (n=2262); those in the second cohort were born in 1915 and assessed at age 95 years (n=1584). All cohort members were eligible irrespective of type of residence. Both cohorts were assessed by surveys that used the same design and assessment instrument, and had almost identical response rates (63%). Cognitive functioning was assessed by mini-mental state examination and a composite of five cognitive tests that are sensitive to age-related changes. Physical functioning was assessed by an activities of daily living score and by physical performance tests (grip strength, chair stand, and gait speed). FINDINGS The chance of surviving from birth to age 93 years was 28% higher in the 1915 cohort than in the 1905 cohort (6·50% vs 5·06%), and the chance of reaching 95 years was 32% higher in 1915 cohort (3·93% vs 2·98%). The 1915 cohort scored significantly better on the mini-mental state examination than did the 1905 cohort (22·8 [SD 5·6] vs 21·4 [6·0]; p<0·0001), with a substantially higher proportion of participants obtaining maximum scores (28-30 points; 277 [23%] vs 235 [13%]; p<0·0001). Similarly, the cognitive composite score was significantly better in the 1915 than in the 1905 cohort (0·49 [SD 3·6] vs 0·01 [SD 3·6]; p=0·0003). The cohorts did not differ consistently in the physical performance tests, but the 1915 cohort had significantly better activities of daily living scores than did the 1905 cohort (2·0 [SD 0·8] vs 1·8 [0·7]; p<0·0001). INTERPRETATION Despite being 2 years older at assessment, the 1915 cohort scored significantly better than the 1905 cohort on both the cognitive tests and the activities of daily living score, which suggests that more people are living to older ages with better overall functioning. FUNDING Danish National Research Foundation; US National Institutes of Health-National Institute on Aging; Danish Agency for Science, Technology and Innovation; VELUX Foundation.

Centenarians - a useful model for healthy aging?: A 29 year follow-up of hospitalizations among 40,000 Danes born in 1905

Centenarians surpass the current human life expectancy with about 20–25 years. However, whether centenarians represent healthy aging still remains an open question. Previous studies have been hampered by a number of methodological shortcomings such as a cross‐sectional design and lack of an appropriate control group. In a longitudinal population‐based cohort, it was examined whether the centenarian phenotype may be a useful model for healthy aging. The study was based on a complete follow up of 39 945 individuals alive in the Danish 1905 birth cohort on January 1, 1977 identified through the Danish Civil Registration System (DCRS). Data from the Danish Demographic Database and The Danish National Patient Register (in existence since 1977) were used. The 1905 cohort was followed up from 1977 through 2004 with respect to hospitalizations and number of hospital days. Survival status was available until December 2006. Danish centenarians from the 1905 cohort were hospitalized substantially less than their shorter‐lived contemporaries at the same point in time during the years 1977 through 2004. For example, at age 71–74, the proportion of nonhospitalized centenarians was 80.5% compared with 68.4% among individuals who died in their early 80s. This trend was evident in both sexes. As a result of their lower hospitalization rates and length of stay in hospital compared with their contemporaries, who died at younger ages, Danish centenarians represent healthy agers. Centenarians constitute a useful study population in the search for fixed traits associated with exceptional longevity, such as genotype.

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.

The male-female health-survival paradox: a survey and register study of the impact of sex-specific selection and information bias.

PURPOSE This study examined whether the health-survival paradox could be due partially to sex-specific selection and information bias in surveys. METHODS The study is based on the linkage of three population-based surveys of 15,330 Danes aged 46-102 years with health registers covering the total Danish population regarding hospitalizations within the last 2 years and prescription medicine within 6 months before the baseline surveys. RESULTS Men had higher participation rates than women at all ages. Hospitalized women and women taking medications had higher participation rate compared with nonhospitalized women (difference=0.7%-3.0%) and female nonusers (difference=0.8%-7.6%), respectively, whereas no consistent pattern was found among men according to hospitalization or medication use status. Men used fewer medications than women, but they underreported medication use to a similar degree as did women. CONCLUSIONS Hospitalized women, as well as women using prescription medicine, were slightly overrepresented in the surveys. Hence, the study found some evidence that selection bias in surveys may contribute to the explanation of the health-survival paradox, but its contribution is likely to be small. However, there was no evidence for sex-specific reporting of medication use among study participants.

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.

Sex Differences in the Level and Rate of Change of Physical Function and Grip Strength in the Danish 1905-Cohort Study

Objectives: The study was conducted to examine sex differences in the initial level and rate of change in physical function and grip strength. Method: The baseline survey included 2,262 Danes born in 1905 and alive in 1998 and followed-up in 2000, 2003, and 2005. Hence, the authors fully used the power of having a cohort with multiple assessments in late life and virtually complete follow-up of lifespan (through December 2008). Latent growth curve modeling was used. Results: Men had higher initial levels and rates of decline in strength score and grip strength. Lifespan was positively correlated with intercepts and slopes. Discussion: The Danish data suggested that the longest-living individuals have higher initial levels of strength score and grip strength and smaller rate of change. The data further suggested that the initial level of strength score and grip strength was more predictive of mortality than the rate of change was, and the predictive effects were similar in men and women.

The Male-Female Health-Survival Paradox and Sex Differences in Cohort Life Expectancy in Utah, Denmark and Sweden 1850-1910

PURPOSE In Utah, the prevalence of unhealthy male risk behaviors are lower than in most other male populations, whereas women experience higher mortality risk because of higher fertility rates. Therefore, we hypothesize that the Utah sex differential in mortality would be small and less than in Sweden and Denmark. METHODS Life tables from Utah, Denmark, and Sweden were used to calculate cohort life expectancies for men and women born in 1850-1910. RESULTS The sex difference in cohort life expectancy was similar or larger in Utah when compared with Denmark and Sweden. The change over time in the sex differences in cohort life expectancy was approximately 2 years smaller for active Mormons in Utah than for other groups suggesting lifestyle as an important component for the overall change seen in cohort life expectancy. Sex differences in cohort life expectancy at the age of 50 years were similar for individuals actively affiliated with the Church of Jesus Christ of Latter-day Saints and for Denmark and Sweden. CONCLUSIONS The hypothesis that a smaller sex difference in cohort life expectancies in Utah would be detected in relation to Denmark and Sweden was not supported. In Utah, the male-female differences in life expectancy remain substantial pointing toward biological mechanisms or other unmeasured risk factors.

Sex differential in mortality trends of old-aged Danes: a nation wide study of age, period and cohort effects

Objective Over the last half century the mortality rates in Denmark for females above age 80 have declined dramatically whereas the decline for males have been modest, resulting in a change in sex-ratio for centenarians from 2 to 5. Here we investigate whether this mortality pattern is mainly explained by period effects, cohort effects or both. This can provide clues for where to search for causes behind the changes in sex differential in mortality seen in many Western countries during the last decades. Methods Age-period-cohort study of mortality for all Danish women and men aged 79–98 during the period 1949–2006. Outcome measures Relative risks for deaths and second order differences for exploration of the nonlinear variation. Results Both the overall trends in mortality differences and the fluctuations in mortality for both men and women were better explained by period effects than by cohort effects. The observed rates were better described by the age, period and cohort model than by other models. Conclusions Our results suggest that causes for both the overall increased difference in mortality and the short term fluctuations in mortality rates are primarily to be found in the period dimension. Cohort effects on the mortality of the oldest Danish women and men played a significant but minor role compared to period effects.

Gender‐specific patterns in age‐related decline in general health among Danish and Chinese: A cross‐national comparative study

Aim:  Studies carried out in Western populations have shown age‐related changes in multiple health domains together with gender‐specific patterns. By focusing on five health domains, self‐rated health, hand grip strength, sit‐to‐stand test, cognitive performance and depression, we examined the age trajectories in general health in a cross‐sectional Chinese sample representing the worlds largest ethnic population and compare with Danish data that represent Western populations in developed countries.