Cohort Life Expectancy Research Articles

Life Expectancy in a Large Cohort of Type 2 Diabetes Patients Treated in Primary Care (ZODIAC-10)

BackgroundMost longitudinal studies showed increased relative mortality in individuals with type 2 diabetes mellitus until now. As a result of major changes in treatment regimes over the past years, with more stringent goals for metabolic control and cardiovascular risk management, improvement of life expectancy should be expected. In our study, we aimed to assess present-day life expectancy of type 2 diabetes patients in an ongoing cohort study.Methodology and Principal FindingsWe included 973 primary care type 2 diabetes patients in a prospective cohort study, who were all participating in a shared care project in The Netherlands. Vital status was assessed from May 2001 till May 2007. Main outcome measurement was life expectancy assessed by transforming actual survival time to standardised survival time allowing adjustment for the baseline mortality rate of the general population. At baseline, mean age was 66 years, mean HbA1c 7.0%. During a median follow-up of 5.4 years, 165 patients died (78 from cardiovascular causes), and 17 patients were lost to follow-up. There were no differences in life expectancy in subjects with type 2 diabetes compared to life expectancy in the general population. In multivariate Cox regression analyses, concentrating on the endpoints ‘all-cause’ and cardiovascular mortality, a history of cardiovascular disease: hazard ratio (HR) 1.71 (95% confidence interval (CI) 1.23–2.37), and HR 2.59 (95% CI 1.56–4.28); and albuminuria: HR 1.72 (95% CI 1.26–2.35), and HR 1.83 (95% CI 1.17–2.89), respectively, were significant predictors, whereas smoking, HbA1c, systolic blood pressure and diabetes duration were not.ConclusionsThis study shows a normal life expectancy in a cohort of subjects with type 2 diabetes patients in primary care when compared to the general population. A history of cardiovascular disease and albuminuria, however, increased the risk of a reduction of life expectancy. These results show that, in a shared care environment, a normal life expectancy is achievable in type 2 diabetes patients.

Solar activity during gestation does not affect human lifespan: evidence from national data

Human lifespan has been reported to relate to solar activity during prenatal development. The likely key mechanism behind this association is increased mutagenic ultraviolet (UVB) radiation during high solar activity that damages DNA. Here, the aim was to replicate the findings of those previous few studies that have suggested a reduced lifespan of individuals born during the years of high solar activity, measured as the sunspot numbers. We used data on annual cohort life expectancy at birth of both women and men born between 1751 and 1915, obtained from ten nations located mainly in Europe. These data, however, provided no evidence that human life expectancy at birth was related to solar activity during gestation among the countries studied.

Do Cohort Mortality Trends Emigrate? Insights on The U.K.'s Golden Cohort From A Comparison with a British Settler Country

ABSTRACTThe assumed rate of future mortality improvement has increased over three recent sets of the United Kingdom's national population projections. This optimism has not been so marked in countries which share ancestors with the U.K. population. New Zealand is one such country that provides a data-rich case example in which to investigate the portability of mortality trends.This paper compares mortality trends in New Zealand with those in England & Wales. Both countries seem to have a ‘golden cohort’ which enjoys faster improving mortality than people born before or after. The birth of the golden cohort in England & Wales coincided with cohort life expectancy there catching up with New Zealand's.We show that first generation migrants from the U.K. have better mortality than New Zealand born residents likely to have British ancestry. The advantage lasts into older ages, decades after migration. We hypothesise that migrants from the U.K.'s golden cohort brought with them an early life mortality improvement advantage, and additionally benefited from the healthier environment of New Zealand at middle to older ages. Further, given the recent strong mortality improvement in New Zealand, the U.K.'s assumptions for future mortality look relatively optimistic.

Distribution of the random future life expectancies in log-bilinear mortality projection models

Projected life tables are obtained from forecasting methods and account for future improvements in longevity. Since the future path of mortality is unknown, working with projected life tables makes the survival probabilities stochastic. The resulting demographic indicators in turn become random variables. This paper aims to study the distribution of period and cohort life expectancies derived from projected life tables. To fix the ideas, we adopt here the standard Lee-Carter framework, where the future forces of mortality are decomposed in a log-bilinear way. Exact formulas are derived for period life expectancies, and approximations are proposed for cohort life expectancies. In the latter case, numerical illustrations based on Belgian population data show that the relative accuracy is remarkable.

Future life expectancy in Australia, Europe, Japan and North America

Human life expectancy has risen in most developed countries over the last century, causing the observed demographic shifts. Babel, Bomsdorf and Schmidt (forthcoming) introduce a stochastic mortality model using panel data procedures which distinguishes between a common time effect and a common age effect of mortality evolvement. Using this mortality model, the present paper provides forecasts of future life expectancy for 17 countries divided into 12 regions: Australia, Alps, Bene, Canada, England and Wales, France, Germany, Italy, Japan, Spain, Scandinavia and the United States of America. We consider (traditional) period life expectancies as well as cohort life expectancies, the latter being a more realistic approach but less common. It turns out that a continuing increase of life expectancy is expected in all considered countries. Further, we show that the probabilistic uncertainty of forecast life expectancies is different if either period life expectancies or cohort life expectancies are considered and, moreover, the uncertainty increases substantially if the error of parameter estimation is included.

Estimating health-adjusted life expectancy conditional on risk factors: results for smoking and obesity

BackgroundSmoking and obesity are risk factors causing a large burden of disease. To help formulate and prioritize among smoking and obesity prevention activities, estimations of health-adjusted life expectancy (HALE) for cohorts that differ solely in their lifestyle (e.g. smoking vs. non smoking) can provide valuable information. Furthermore, in combination with estimates of life expectancy (LE), it can be tested whether prevention of obesity and smoking results in compression of morbidity.MethodsUsing a dynamic population model that calculates the incidence of chronic disease conditional on epidemiological risk factors, we estimated LE and HALE at age 20 for a cohort of smokers with a normal weight (BMI < 25), a cohort of non-smoking obese people (BMI>30) and a cohort of 'healthy living' people (i.e. non smoking with a BMI < 25). Health state valuations for the different cohorts were calculated using the estimated disease prevalence rates in combination with data from the Dutch Burden of Disease study. Health state valuations are multiplied with life years to estimate HALE. Absolute compression of morbidity is defined as a reduction in unhealthy life expectancy (LE-HALE) and relative compression as a reduction in the proportion of life lived in good health (LE-HALE)/LE.ResultsEstimates of HALE are highest for a 'healthy living' cohort (54.8 years for men and 55.4 years for women at age 20). Differences in HALE compared to 'healthy living' men at age 20 are 7.8 and 4.6 for respectively smoking and obese men. Differences in HALE compared to 'healthy living' women at age 20 are 6.0 and 4.5 for respectively smoking and obese women. Unhealthy life expectancy is about equal for all cohorts, meaning that successful prevention would not result in absolute compression of morbidity. Sensitivity analyses demonstrate that although estimates of LE and HALE are sensitive to changes in disease epidemiology, differences in LE and HALE between the different cohorts are fairly robust. In most cases, elimination of smoking or obesity does not result in absolute compression of morbidity but slightly increases the part of life lived in good health.ConclusionDifferences in HALE between smoking, obese and 'healthy living' cohorts are substantial and similar to differences in LE. However, our results do not indicate that substantial compression of morbidity is to be expected as a result of successful smoking or obesity prevention.

Relationships between period and cohort life expectancy: Gaps and lags

This paper offers an empirical and analytic foundation for regarding period life expectancy as a lagged indicator of the experience of real cohorts in populations experiencing steady improvement in mortality. We find that current period life expectancy in the industrialized world applies to cohorts born some 40–50 years ago. Lags track an average age at which future years of life are being gained, in a sense that we make precise. Our findings augment Ryder's classic results on period–cohort translation.

Secondary sex ratios and male lifespan: damaged or culled cohorts.

Population stressors reportedly reduce the human secondary sex ratio (i.e., the odds of a newborn's being male) by, among other mechanisms, inducing the spontaneous abortion of males who would have been born live had mothers not been stressed. Controversy remains as to whether these abortions result from reduced maternal tolerance of males at the low end of a relatively constant distribution of survivability (i.e., the "culled cohort" explanation) or from shifts in the whole distribution of survivability such that more males fall below a relatively constant criterion of maternal tolerance for low survivability (i.e., the "damaged cohort" explanation). These alternatives make opposing predictions regarding the relationship between the secondary sex ratio and lifespan of male birth cohorts. We test the hypothesis that the secondary sex ratio among Swedish cohorts born in the years 1751 through 1912 predicts male cohort life expectancy at birth (i.e., realized lifespan). Our results support the culled cohort argument. We argue that these findings have implications for the basic literature concerned with temporal variation in the secondary sex ratio, for more applied work concerned with the fetal origins of adult health, and for pubic health surveillance.

Changing mortality and average cohort life expectancy

Period life expectancy varies with changes in mortality, and should not be confused with the life expectancy of those alive during that period. Given past and likely future mortality changes, a recent debate has arisen on the usefulness of the period

Should Resistance Testing Be Performed for Treatment-Naive HIV-Infected Patients? A Cost-Effectiveness Analysis

Data from the United States and Europe show a population prevalence of baseline drug resistance of 8%-10% among human immunodeficiency virus (HIV)-infected patients who are antiretroviral naive. Our objective was to determine the clinical impact and cost-effectiveness of genotype resistance testing for treatment-naive patients with chronic HIV infection. We utilized a state-transition model of HIV disease to project life expectancy, costs, and cost-effectiveness in a hypothetical cohort of antiretroviral-naive patients with chronic HIV infection. On the basis of a US survey of treatment-naive patients from the Centers for Disease Control and Prevention, we used a baseline prevalence of drug resistance of 8.3%. A strategy of genotype-resistance testing at initial diagnosis of HIV infection increased per-person quality-adjusted life expectancy by 1.0 months, with an incremental cost-effectiveness ratio of 23,900 dollars per quality-adjusted life-year gained, compared with no genotype testing. The cost-effectiveness ratio for resistance testing remained less than 50,000 dollars per quality-adjusted life-year gained, unless the prevalence of resistance was < or =1%, a level lower than those reported in most regions of the United States and Europe. In sensitivity analyses, the cost-effectiveness remained favorable through wide variations in baseline assumptions, including variations in genotype cost, prevalence of resistance overall and to individual drug classes, and sensitivity of resistance testing. Genotype-resistance testing of chronically HIV-infected, antiretroviral-naive patients is likely to improve clinical outcomes and is cost-effective, compared with other HIV care in the United States. Resistance testing at the time of diagnosis should be the standard of care.

Life expectancy in a birth cohort of Boxers followed up from weaning to 10 years of age

To determine mortality rate over time, risk factors for death, and heritability of life expectancy in Boxers. 1,733 purebred Boxers born in The Netherlands between January 1994 and March 1995. Dogs were followed up from weaning (ie, 49 days of age) to 10 years of age through use of a written questionnaire sent to owners every 6 months. Mortality rate over time, risk factors potentially associated with death, and heritability of life expectancy were examined by use of a proportional hazards model based on the Weibull distribution. stimated mortality rate during the 10-year study period for this birth cohort of Boxers was 45%. The probability of surviving to 5 years of age was 88%; the probability of surviving to 10 years of age was 55%. Estimated effective heritability of life expectancy was 0.076, meaning that in this population, an estimated 76% of the observed variation in life expectancy could be attributed to genetic differences among dogs that were passed from parents to their offspring. Results suggest that cumulative incidence of death from weaning to 10 years of age among this birth cohort of Boxers was 45%. The estimated heritability of life expectancy suggested that life expectancy can be improved by use of selective breeding.

Age-specific contributions to changes in the period and cohort life expectancy

Period life expectancy has increased more slowly than its cohort counterpart. This paper explores the differences between life expectancies at a given time (the gap) and the time required for period life expectancy to reach the current level of cohort

The effect of World War I and the 1918 influenza pandemic on cohort life expectancy of South Australian males born in 1881–1900

Cohort lifetime distribution functions have been estimated for the twenty separate calendar year cohorts of South Australian males born in 1881–1900. A cohort life expectancy at birth was calculated from each of these distribution functions, and a composite assessment made of the reduction in cohort life expectancy at birth due to both World War I 1914–1918 and the 1918 Influenza Pandemic. By partitioning each cohort, the cohort life expectancy at birth of the subgroup that had overseas military service is estimated to be 85 to 90 per cent of the cohort life expectancy at birth of the subgroup that remained in South Australia.

Screening for Lung Cancer With CT: A Preliminary Cost-effectiveness Analysis

To appraise the potential cost-effectiveness of lung cancer screening with CT.Incremental cost-effectiveness ratios are estimated for two hypothetical cohorts followed up over time. One cohort was screened over the first 5 years of the study period; the other cohort received usual care. Cost streams are projected for each cohort under alternative sets of parameters/ assumptions and from the perspective of national payer groups. Cohort cost differentials arise as a result of screening and variations in stage-specific treatment. Cohort life expectancies are also projected, and they too differ as a consequence of variations in the stage distribution at diagnosis. The ratios of these cost and life-expectancy differences are used to judge the expected economic value of screening.Results are analyzed for a "worst-case" scenario, ie, with the highest cost and lowest yield assumptions. Under these conditions, screening with CT costs approximately $48,000 per life-year gained, if screening results in 50% of lung cancers detected at localized stage. Smaller proportions of cancer detected at a localized stage result in higher cost-effectiveness ratios, and vice versa.If screening for lung cancer is effective, it is likely to be cost-effective if the screening process can detect > 50% of cancers at localized stage.

Social Security Reform with a Focus on the Netherlands

The essay discusses the general issues of labor market incentives and of adapting to the trend to longer lives, including legislated adaptations in Chile, Italy, Sweden, and the US. For the Netherlands there are two concrete proposals – that the AOW fund hold a diversified portfolio and that workers have the option of delaying the start of AOW benefits in order to receive larger benefits for themselves and surviving spouses. Three issues are identified for evaluation and monitoring: whether widow benefits from private pensions might become too small in the future (given the introduction of choice between higher worker benefits and survivor benefits), whether final-pay pensions should be modified to indexed career-average pensions (to improve labor mobility and fairness), and whether there should be some automatic adjustments for cohort life expectancy.

MULTIDIMENSIONAL DISABILITY/MORTALITY TRAJECTORIES AT AGES 65 AND OVER: THE IMPACT OF STATE DEPENDENCE

How dependent is life expectancy atage 65 on one’s degree of disability or specific typesof functional limitations? Are there significant sexdifferences? For closed-cohorts of males and femalesin different disability/functional-status states atage 65, how do their age and disability-specificfunctional statuses evolve with increasing age? Thesequestions are addressed by analyzing multidimensionaldisability/mortality trajectories generated using atwo-component stochastic process model applied tomultivariate longitudinal data from the 1982 to 1994National Long Term Care Surveys. In this model, onecomponent process describes the temporal and agedynamics of a person’s functional state and the otherdescribes the risk of death as a function of aperson’s age and stochastically evolving position inthe functional-status state space. Large differenceswere found in life expectancy among closed cohorts ofpersons who, at age 65, are in one of seven basicdisability/functional-status states, identified by amultivariate analysis. Large differences betweenmales and females in life expectancy for theorigin-specific cohorts were also found. Whilefemales starting in most states tend to live longer,they are not as likely to return to the healthy,nondisabled state – females also tend to go intoinstitutions at a higher rate than males.

High intraocular pressure and survival: the Framingham studies

PURPOSE: To examine whether high intraocular pressure (greater than or equal to 25 mm Hg) or a history of treatment for glaucoma is associated with decreased survival and, if so, how such ocular markers might be explained. METHODS: Eye examinations, including applanation tonometry, were conducted on members of the Framingham Eye Study cohort from February 1, 1973, to February 1, 1975. Participants who reported a history of treatment for glaucoma were identified. Survival data, including information on the date of death, were available from the time of the Eye Study through March 31, 1990. RESULTS: Of the 1,764 persons under the age of 70 years at the baseline eye examination, 1,421 persons had low intraocular pressure (≤20 mm Hg), 264 persons had medium intraocular pressure levels (20 to 24 mm Hg), and 79 persons had high intraocular pressure (≥25 mm Hg) or history of glaucoma treatment. During the follow-up period, 29%, 30%, and 47% died in the groups with low, medium, and high intraocular pressure (or history of glaucoma treatment), respectively. In an age-and-sex adjusted Cox proportional hazards analysis, the death rate ratio for the group with medium intraocular pressure relative to the group with low intraocular pressure was 1.04. The corresponding death rate ratio for the group with high intraocular pressure was 1.56 with a 95% confidence interval of 1.11 to 2.19 ( P < .001). After adjustment for age, sex, hypertension, diabetes, cigarette smoking, and body mass index, a positive relationship remained, but at a borderline level of significance ( P = .075). CONCLUSIONS: High intraocular pressure or the presence of glaucoma is a marker for decreased life expectancy in the Framingham Eye Study cohort. The relationship is present even after adjustment for risk factors known to be associated with higher mortality such as age, sex, hypertension, diabetes, cigarette smoking, and body mass index. Special attention to the general health status of patients with high intraocular pressure or glaucoma seems warranted.

Estimating life expectancy using an age-cohort model in Taiwan.

Life expectation is a valuable summary index in public health and actuarial science. The life expectancies published in the vital statistics, however, are derived from the "current" rather than from the "cohort" life table. The former is based on a strong assumption of constant mortality in the population, whereas the latter calls for a recording of the mortality experience of a group of individuals, which is often an impossible task. Thus, a method of calculating cohort life expectancy without actual follow up is much needed. Estimation of cohort life expectancy was based on an age-cohort model. Mortality data for the male population in Taiwan from 1951 to 1990 are used to illustrate the methodology. The increment of life expectancy over time in Taiwan is actually steeper than was previously thought using the current life table technique. The method is easy to implement and the data required are the usual age and period cross classified mortality data. It warrants further investigation.

Management of unruptured intracranial arteriovenous malformations: a decision analysis.

The management of unruptured intracranial arteriovenous malformations (AVMs) is controversial. Some authorities favor elective excision of the AVM before it bleeds, whereas others advise nonintervention unless the AVM bleeds, at which time surgical excision is performed in those who survive. A Markov model was developed that stimulates a clinical trial in which cohorts of patients with unruptured AVMs were assigned to either elective excision of their AVMs or conservative treatment (unless the AVM bled). Incremental utilities for both strategies were calculated at the end of each year after the beginning of the trial and are expressed as quality and risk-adjusted life years. The process was continued until all members of the cohorts had died. The mean quality and risk-adjusted life expectancy for members of a cohort was calculated by dividing the total number of quality and risk-adjusted life years the cohort had accumulated by the size of the cohort. If the baseline values for surgical complications were used in the computation, the quality and risk-adjusted life expectancy for the surgical cohorts was at least 1 quality and risk-adjusted life year greater than for nonsurgical cohorts up to age 44. If a more favorable complication rate were used, elective surgery could benefit selected patients in their early 60s when the location and configuration of the AVM was favorable. Elective surgical resection is justified in many instances before rupture, particularly in young patients who have intracranial AVMs that have a favorable location, size, and venous drainage.

Bleach programs for preventing AIDS among i.v. drug users: modeling the impact of HIV prevalence.

The growing importance of drug use as a mode of HIV transmission has led to increased attention to AIDS prevention among intravenous drug users (IVDUs). This analysis examines the effectiveness of bleach distribution, a program to prevent HIV transmission via shared needles. We used a Markov model to assess the role of the initial HIV prevalence among drug users in determining the effectiveness of bleach programs. The model incorporates survey data on risk behaviors and published information describing HIV incubation and mortality. It predicts life expectancy for cohorts of IVDUs with and without a bleach program to estimate program effectiveness. We found that bleach programs can produce the greatest life-year savings in areas of low HIV prevalence. In the lowest prevalence scenario (0.02 initial prevalence), initiation of the program resulted in a projected savings of 2.3 life years per HIV-negative drug user, compared with 1.7 and 1.3 years under medium (0.25) and high (0.60) prevalence, respectively. While bleach programs are beneficial in all groups of IVDUs, these results highlight the advantages of introducing bleach programs early, when prevalence is still comparatively low in a drug-user population.