Limitless longevity: comment on the Contribution of rectangularization to the secular increase of life expectancy

Focus on disability-free life expectancy: implications for health-related quality of life

BACKGROUND

Since the end of the industrial revolution, advances in public health and clinical medicine have contributed to dramatic decreases in infant and childhood mortality, improvements in health-related quality of life (HRQoL), increases in overall life expectancy (LE), and rectangularization of survival curves.

OBJECTIVES

In this article, we focus on disability that has occurred with the overall lengthening of LE in many populations and the implications this has for decreased HRQoL.

METHODS

We utilize the concept of rectangularization of population survival to depict the rising prevalence of disability associated with increased LE, especially among racial and ethnic minorities and people of low socioeconomic status (SES) and relate this to HRQoL.

RESULTS

Disability-free life expectancy (DFLE) and healthy life expectancy (HLE) are defined in terms of HRQoL. Specific attention is focused on disability experienced by disparate populations around the globe. By focusing on disparities in DFLE, and the need to expand LE to include HLE as a central component of HRQoL, this work provides an important counterpoint to the attention that has been paid to LE disparities according to race, gender, ethnicity, education, and SES.

DISCUSSION

By calling attention to those factors that appear to be the most important drivers of the differences in quality and length of DFLE between different groups (i.e., the components of the social gradient, exposure to chronic stress, systemic inflammation, and the psychological and biological mechanisms associated with the gut-brain axis) and, by logical extension, HRQoL, we hope to promote research in this arena with the ultimate goal of improving DFLE, HLE, and overall HRQoL, especially in disparate populations around the globe.

How long do centenarians survive? Life expectancy and maximum lifespan

OBJECTIVES

The purpose of this study was to explore the pattern of mortality above the age of 100 years. In particular, we aimed to examine whether Scandinavian data support the theory that mortality reaches a plateau at particularly old ages. Whether the maximum length of life increases with time was also investigated.

METHODS

The analyses were based on individual level data on all Swedish and Danish centenarians born from 1870 to 1901; in total 3006 men and 10 963 women were included. Birth cohort-specific probabilities of dying were calculated. Exact ages were used for calculations of maximum length of life. Whether maximum age changed over time was analysed taking into account increases in cohort size.

RESULTS

The results confirm that there has not been any improvement in mortality amongst centenarians in the past 30 years and that the current rise in life expectancy is driven by reductions in mortality below the age of 100 years. The death risks seem to reach a plateau of around 50% at the age 103 years for men and 107 years for women. Despite the rising life expectancy, the maximum age does not appear to increase, in particular after accounting for the increasing number of individuals of advanced age.

CONCLUSION

Mortality amongst centenarians is not changing despite improvements at younger ages. An extension of the maximum lifespan and a sizeable extension of life expectancy both require reductions in mortality above the age of 100 years.

Does a hospital admission in old age denote the beginning of life with a compromised health-related quality of life? A longitudinal study of men and women aged 65 years and above participating in the Stockholm Public Health Cohort

OBJECTIVES

The objective of this study was to analyse how hospitalisation after the age of 60 affected individuals' health-related quality of life (HRQoL). The main hypothesis was that a hospital admission in old age can be seen as a proxy of ill health and possibly as a health divider, separating life into a healthy and an unhealthy part. The extent to which this is true depends on which disease individuals face and how functional ability and HRQoL are affected.

SETTINGS

This was a longitudinal study, based on an older cohort of individuals who participated in the Stockholm Public Health Cohort (SPHC) survey in 2006; the survey took place in Stockholm, Sweden. Information regarding hospitalisations and deaths, which is available through Swedish administrative registers, was linked to the survey from the National Patient Register and Cause of Death Register.

PARTICIPANTS

2101 individuals, 65+ years old at inclusion, with no previous hospitalisations at baseline (2006), were followed for 4 years until 2010 (end of follow-up).

PRIMARY AND SECONDARY OUTCOME MEASURES

HRQoL was assessed through a utility index derived from the EuroQol 5D questionnaire, at baseline and at 2010. The change in HRQoL after admission(s) to the hospital was estimated as the difference between the 2010 and 2006 levels using linear regression, also considering several covariates.

RESULTS

A single hospitalisation did not reduce individuals' HRQoL, either for men or women. On the other hand, multiple any-cause hospitalisations reduced HRQoL between 3.2% and 6.5%. When looking into hospitalisations for specific causes, such as hip fractures, a decrease in HRQoL was observed as well; however, conclusions regarding this were impeded by the small sample size.

CONCLUSIONS

Hospital admissions in old age may indicate a shift from a healthy life to a life of compromised health when considering their frequency and cause over a period of time.

Biodemography of old-age mortality in humans and rodents

The growing number of persons living beyond age 80 underscores the need for accurate measurement of mortality at advanced ages and understanding the old-age mortality trajectories. It is believed that exponential growth of mortality with age (Gompertz law) is followed by a period of deceleration, with slower rates of mortality increase at older ages. This pattern of mortality deceleration is traditionally described by the logistic (Kannisto) model, which is considered as an alternative to the Gompertz model. Mortality deceleration was observed for many invertebrate species, but the evidence for mammals is controversial. We compared the performance (goodness-of-fit) of two competing models-the Gompertz model and the logistic (Kannisto) model using data for three mammalian species: 22 birth cohorts of U.S. men and women, eight cohorts of laboratory mice, and 10 cohorts of laboratory rats. For all three mammalian species, the Gompertz model fits mortality data significantly better than the "mortality deceleration" Kannisto model (according to the Akaike's information criterion as the goodness-of-fit measure). These results suggest that mortality deceleration at advanced ages is not a universal phenomenon, and survival of mammalian species follows the Gompertz law up to very old ages.

New Developments in the Biodemography of Aging and Longevity

Biodemography is a promising scientific approach based on using demographic data and methods for getting insights into biological mechanisms of observed processes. Recently, new important developments have happened in biodemographic studies of aging and longevity that call into question conventional aging theories and open up novel research directions. Recent studies found that the exponential increase of the mortality risk with age (the famous Gompertz law) continues even at extreme old ages in humans, rats, and mice, thus challenging traditional views about old-age mortality deceleration, mortality leveling-off, and late-life mortality plateaus. This new finding represents a challenge to many aging theories, including the evolutionary theory that explains senescence by a declining force of natural selection with age. Innovative ideas are needed to explain why exactly the same exponential pattern of mortality growth is observed not only at reproductive ages, but also at very-old postreproductive ages (up to 106 years), long after the force of natural selection becomes negligible (when there is no room for its further decline). Another important recent development is the discovery of long-term 'memory' for early-life experiences in longevity determination. Siblings born to young mothers have significantly higher chances to live up to 100 years, and this new finding, confirmed by two independent research groups, calls for its explanation. As recent studies found, even the place and season of birth matter for human longevity. Beneficial longevity effects of young maternal age are observed only when children of the same parents are compared, while the maternal age effect often could not be detected in across-families studies, presumably being masked by between-family variation. It was also found that male gender of centenarian has a significant positive effect on the survival of adult male biological relatives (brothers and fathers) but not of female relatives. Finally, large gender differences are found in longevity determinants for males and females, suggesting a higher importance of occupation history for male centenarians as well as a higher importance of home environment history for female centenarians.

Does improved survival lead to a more fragile population: time trends in second and third hospital admissions among men and women above the age of 60 in Sweden

Background

Life expectancy and time to first hospitalization have been prolonged, indicating that people live longer without needing hospital care. Life expectancy increased partially due to improved survival from severe diseases, which, however, could lead to a more fragile population. If so, time to a subsequent hospitalization could decrease. Alternatively, the overall trend of improved health could continue after the first hospitalization, prolonging also the time to subsequent hospitalizations. This study analyzes trends in subsequent hospitalizations among Swedish men and women above the age of 60, relating them to first hospitalization. It also looks at trends in the proportion of never hospitalized.

Methods

Individuals were followed in national registers for hospital admissions and deaths between 1972 and 2010. The proportion of never hospitalized individuals at given ages and time points, and the annual change in the risks of first and subsequent hospitalizations, were calculated.

Findings

An increase in the proportion of never hospitalized was seen over time. The risks of first as well as subsequent hospitalizations were reduced by almost 10% per decade for both men and women. Improvements were observed mainly for individuals below the ages of 90 and up to the year 2000.

Conclusions

The reduction in annual risk of both first and subsequent hospitalizations up to 90 years of age speaks in favor of a postponement of the overall morbidity among the elderly and provides no support for the hypothesis that the population becomes more fragile due to increased survival from severe diseases.

Losing ground--Swedish life expectancy in a comparative perspective

BACKGROUND

In the beginning of the 1970s, Sweden was the country where both women and men enjoyed the world's longest life expectancy. While life expectancy continues to be high and increasing, Sweden has been losing ground in relation to other leading countries.

METHODS

We look at life expectancy over the years 1970-2008 for men and women. To assess the relative contributions of age, causes of death, and smoking we decompose differences in life expectancy between Sweden and two leading countries, Japan and France. This study is the first to use this decomposition method to observe how smoking related deaths contribute to life expectancy differences between countries.

RESULTS

Sweden has maintained very low mortality at young and working ages for both men and women compared to France and Japan. However, mortality at ages above 65 has become considerably higher in Sweden than in the other leading countries because the decrease has been faster in those countries. Different trends for circulatory diseases were the largest contributor to this development in both sexes but for women also cancer played a role. Mortality from neoplasms has been considerably low for Swedish men. Smoking attributable mortality plays a modest role for women, whereas it is substantially lower in Swedish men than in French and Japanese men.

CONCLUSIONS

Sweden is losing ground in relation to other leading countries with respect to life expectancy because mortality at high ages improves more slowly than in the leading countries, especially due to trends in cardiovascular disease mortality. Trends in smoking rates may provide a partial explanation for the trends in women; however, it is not possible to isolate one single explanatory factor for why Sweden is losing ground.

Mortality Trajectories at Extreme Old Ages: A Comparative Study of Different Data Sources on U.S. Old-Age Mortality

The growing number of individuals living beyond age 80 underscores the need for accurate measurement of mortality at advanced ages. Our earlier published study challenged the common view that the exponential growth of mortality with age (Gompertz law) is followed by a period of deceleration, with slower rates of mortality increase (Gavrilov and Gavrilova 2011). This refutation of mortality deceleration was made using records from the U.S. Social Security Administration's Death Master File (DMF). Taking into account the significance of this finding for actuarial theory and practice, we tested these earlier observations using additional independent datasets and alternative statistical approaches. In particular, the following data sources for U.S. mortality at advanced ages were analyzed: (1) data from the Human Mortality Database (HMD) on age-specific death rates for 1890-99 U.S. birth cohorts, (2) recent extinct birth cohorts of U.S. men and women based on DMF data, and (3) mortality data for railroad retirees. In the case of HMD data, the analyses were conducted for 1890-99 birth cohorts in the age range 80-106. Mortality was fitted by the Gompertz and logistic (Kannisto) models using weighted nonlinear regression and Akaike information criterion as the goodness-of-fit measure. All analyses were conducted separately for men and women. It was found that for all studied HMD birth cohorts, the Gompertz model demonstrated better fit of mortality data than the Kannisto model in the studied age interval. Similar results were obtained for U.S. men and women born in 1890-99 and railroad retirees born in 1895-99 using the full DMF file (obtained from the National Technical Information Service, or NTIS). It was also found that mortality estimates obtained from the DMF records are close to estimates obtained using the HMD cohort data. An alternative approach for studying mortality patterns at advanced ages is based on calculating the age-specific rate of mortality change (life table aging rate, or LAR) after age 80. This approach was applied to age-specific death rates for Canada, France, Sweden and the United States available in HMD. It was found that for all 24 studied single-year birth cohorts, LAR does not change significantly with age in the age interval 80-100, suggesting no mortality deceleration in this interval. Simulation study of LAR demonstrated that the apparent decline of LAR after age 80 found in earlier studies may be related to biased estimates of mortality rates measured in a wide five-year age interval. Taking into account that there exists several empirical estimates of hazard rate (Nelson-Aalen, actuarial and Sacher), a simulation study was conducted to find out which one is the most accurate and unbiased estimate of hazard rate at advanced ages. Computer simulations demonstrated that some estimates of mortality (Nelson-Aalen and actuarial) as well as kernel smoothing of hazard rates may produce spurious mortality deceleration at extreme ages, while the Sacher estimate turns out to be the most accurate estimate of hazard rate. Possible reasons for finding apparent mortality deceleration in earlier studies are also discussed.

Age-specific trends in morbidity, mortality and case-fatality from cardiovascular disease, myocardial infarction and stroke in advanced age: evaluation in the Swedish population

Background

It is not clear if the downward trend in cardiovascular disease (CVD) observed for ages up to 85 years can be extended to the oldest old, those 85 years and above.

Methods and Findings

This nationwide cohort study presents age specific trends of CVD as well as for myocardial infarction (MI) and stroke separately for the period 1994 to 2010 for individuals 85 to 99 years old in Sweden. Data were extracted from national registries. All analyses were based on one-year age- and sex- specific figures. The risk for CVD increased with every age above 85 years although the rate of increase leveled off with age. Over time, the risk for CVD and MI decreased for all ages, and for stroke for ages up to 89 years. However, the risk of MI increased until around 2001 in all age groups and both sexes but decreased after that. The overall mortality improved for all outcomes over the period 1994 to 2010, so did the survival within 28 days from an event. The average annual decline in mortality over all ages, 85 and above was 3% for MI, 2% for stroke and for 2% CVD. Corresponding figures for ages 60–84 was 4% for each of MI, stroke and CVD. The results were similar for men and women.

Conclusions

Improvements in CVD risks observed among ages up to 85 years appear to have extended also to ages above 85 years, even if the rate of improvement plateaued with age. The improvements in survival for all ages up to 99 years give no support to the hypothesis that more fragile individuals reach higher ages. Additional research is needed to find out if improvement in survival can be seen also for the second and third event of CVD, stroke and MI.