Objective: Longevity fails to account for health and functional status during aging. We sought to quantify differences in years of total life, years of healthy life, and years of able life among groups defined by age, sex, and race. Design: Primary analysis of a cohort study. Setting: 18 years of annual evaluations in four U.S. communities. Participants: 5888 men and women aged 65 and older. Measurements: Years of life were calculated as the time from enrollment to death or 18 years. Years of total, healthy, and able life were determined from self-report during annual or semi-annual contacts. Cumulative years were summed across each of the age and sex groups. Results: White women had the best outcomes for all three measures, followed by white men, non-white women, and non-white men. For example, at the mean age of 73, a white female participant could expect 12.9 years of life, 8.9 of healthy life and 9.5 of able life, while a non-white female could expect 12.6, 7.0, and 8.0 years, respectively. A white male could expect 11.2, 8.1, and 8.9 years of life, healthy life, and able life, and a non-white male 10.3, 6.2, and 7.9 years. Regardless of starting age, individuals of the same race and sex groups spent similar amounts (not proportions) of time in an unhealthy or unable state. Conclusion: Gender had a greater effect on longevity than did race, but race had a greater effect on years spent healthy or able. The mean number of years spent in an unable or sick state was surprisingly independent of the lifespan.
able life; active life; healthy life; longevity; ADL
Objective: To create personalized estimates of future health and ability status for older adults. Method: Data came from the Cardiovascular Health Study (CHS), a large longitudinal study. Outcomes included years of life, years of healthy life (based on self-rated health), years of able life (based on activities of daily living), and years of healthy and able life. We developed regression estimates using the demographic and health characteristics that best predicted the four outcomes. Internal and external validity were assessed. Results: A prediction equation based on 11 variables accounted for about 40% of the variability for each outcome. Internal validity was excellent, and external validity was satisfactory. The resulting CHS Healthy Life Calculator (CHSHLC) is available at http://healthylifecalculator.org. Conclusion: CHSHLC provides a well-documented estimate of future years of healthy and able life for older adults, who may use it in planning for the future.
demography; mortality; active life/physical activity; clinical gerontology; decision-making; life expectancy/longevity; quality of life
To determine whether elderly people with different patterns of MRI findings have different long-term outcomes.
longitudinal cohort study.
the Cardiovascular Health Study.
5,888 people over age 65 were recruited; 3,660 underwent MRI; and 3,230 without a stroke prior to the scan were included in these analyses.
Cluster analysis of brain MRI findings was previously used to define five clusters: Normal, Atrophy, Simple Infract, Leukoaraiosis, and Complex Infarct. Participates were subsequently classified as "healthy" if they rated their health as excellent, very good or good and as "able" if they did not report any limitations in activities of daily living (ADLs). Mean years of life (YoL), years of healthy life (YHL) and years of able life (YAL) were calculated over 16 years following the MRI and compared across clusters, using unadjusted and adjusted regression analyses.
Mean age of participants was 75.0 years. With 16 years of follow-up, mean YoL was 11.3 years; YHL, 8.0; and YAL, 8.4.Outcomes differed significantly across clusters. With or without adjustments, outcomes were all significantly better in the Normal than Complex Infarct cluster. The three remaining clusters had intermediate results, significantly different from the Normal and Complex Infarct clusters but not usually from one another. Over 16 years of follow-up, participants in the Complex Infarct cluster (n=368) spent the largest percentage of their 8.4 years alive being sick (38%) and not able (38%).
Findings on MRI scans in the elderly are associated not only with long-term survival but also with long-term self-rated health and limitation in ADLs. The combination of infarcts and leukoaraiosis carried the worst prognosis, presumably reflecting small vessel disease.
magnetic resonance imaging; cohort study; prognosis; and outcome assessment
Chronic obstructive lung disease frequently leads to disability. Older patients may transition between disability and independence over time.
To identify factors associated with transitions between disability and independent function in obstructive lung disease.
We analyzed data for 4,394 participants in the Cardiovascular Health Study who completed pre-bronchodilator spirometry. We calculated the 1-year probability of developing and resolving impairment in ≥1 Instrumental Activity of Daily Living (IADL) or ≥1 Activity of Daily Living (ADL) using transition probability analysis. We identified factors associated with resolving disability using relative risk regression.
The prevalence of IADL impairment was higher among moderate (23.9%) and severe (36.9%) airflow obstruction compared to normal spirometry (22.5%; p<0.001). Among participants with severe airflow obstruction, 23.5% recovered independence in IADLs and 40.5% recovered independence in ADLs. In adjusted analyses, airflow obstruction predicted development of IADL, but not ADL impairment. Participants with severe airflow obstruction were less likely to resolve IADL impairment (RR 0.67, 95% CI 0.49-0.94). Compared to the most active persons (≥28 blocks walked per week), walking less was associated with decreased likelihood of resolving IADL impairment (7-27 blocks: RR 0.81, 0.69-0.86, and < 7 blocks: RR 0.73, 0.61 -0.86). Increased strength (RR 1.16, 1.05-1.29) was associated with resolving IADL impairment.
Disability is common in older persons, especially those with severe airflow obstruction. Increased physical activity and muscle strength are associated with recovery. Research on interventions to improve these factors among patients with obstructive lung disease and disability is needed.
chronic airflow obstruction; activities of daily living; disability
The health of older adults declines over time, but there are many ways of measuring health. It is unclear whether all health measures decline at the same rate or whether some aspects of health are less sensitive to aging than others.
We compared the decline in 13 measures of physical, mental, and functional health from the Cardiovascular Health Study: hospitalization, bed days, cognition, extremity
strength, feelings about life as a whole, satisfaction with the purpose of life, self-rated health, depression, digit symbol substitution test, grip strength, activities of daily living, instrumental activities of daily living, and gait speed. Each measure was standardized against self-rated health. We compared the 5-year change to see which of the 13 measures declined the fastest and the slowest.
The 5-year change in standardized health varied from a decline of 12 points (out of 100) for hospitalization to a decline of 17 points for gait speed. In most comparisons, standardized health from hospitalization and bed days declined the least, whereas health measured by activities of daily living, instrumental activities of daily living, and gait speed declined the most. These rankings were independent of age, sex, mortality patterns, and the method of standardization.
All of the health variables declined, on average, with advancing age, but at significantly different rates. Standardized measures of mental health, cognition, quality of life, and hospital utilization did not decline as fast as gait speed, activities of daily living, and instrumental activities of daily living. Public health interventions to address problems with gait speed, activities of daily living, and instrumental activities of daily living may help older adults to remain healthier in all dimensions.
Aging; Cognition; ADL; IADL; Gait.
Little is known about how many years of life and disability-free years seniors can gain through exercise. Using data from the Cardiovascular Health Study, the authors estimated the extra years of life and self-reported healthy life (over 11 years) and years without impairment in activities of daily living (over 6 years) associated with quintiles of physical activity (PA) in older adults from different age groups. They estimated PA from the Minnesota Leisure Time Activities Questionnaire. Multivariable linear regression adjusted for health-related covariates. The relative gains in survival and years of healthy life (YHL) generally were proportionate to the amount of PA, greater among those 75+, and higher in men. Compared with being sedentary, the most active men 75+ had 1.49 more YHL (95% CI: 0.79, 2.19), and the most active women 75+ had 1.06 more YHL (95% CI: 0.44, 1.68). Seniors over age 74 experience the largest relative gains in survival and healthy life from physical activity.
aging; exercise; mortality; health status; activities of daily living
High rates of disability associated with chronic airway obstruction may be caused by impaired pulmonary function, pulmonary symptoms, other chronic diseases, or systemic inflammation.
We analyzed data from the Cardiovascular Health Study, a longitudinal cohort of 5888 older adults. Categories of lung function (normal; restricted; borderline, mild-moderate, and severe obstruction) were delineated by baseline spirometry (without bronchodilator). Disability-free years were calculated as total years alive and without self-report of difficulty performing ≥1 Instrumental Activities of Daily Living over 6 years of follow-up. Using linear regression, we compared disability-free years by lung disease category, adjusting for demographic factors, body mass index, smoking, cognition, and other chronic comorbidities. Among participants with airflow obstruction, we examined the association of respiratory factors (FEV1 and dyspnea) and non-respiratory factors (ischemic heart disease, congestive heart failure, diabetes, muscle weakness, osteoporosis, depression and cognitive impairment) on disability-free years.
The average disability free years were 4.0 out of a possible 6 years. Severe obstruction was associated with 1 fewer disability-free year compared to normal spirometry in the adjusted model. For the 1,048 participants with airway obstruction, both respiratory factors (FEV1 and dyspnea) and non-respiratory factors (heart disease, coronary artery disease, diabetes, depression, osteoporosis, cognitive function, and weakness) were associated with decreased disability-free years.
Severe obstruction is associated with greater disability compared to patients with normal spirometery. Both respiratory and non-respiratory factors contribute to disability in older adults with abnormal spirometry.
Chronic airflow obstruction; instrumental activities of daily living; disability; disablement process
Two-thirds of older adults are currently classified as overweight or obese. Given that the importance of these weight categories was documented primarily in middle-aged persons, the survival and health status consequences for older adults are controversial. Here, we explore the issue of whether weight categories predict subsequent mortality and morbidity in older adults.
Design, Setting, and Participants
Data came from the Cardiovascular Health Study, a population-based cohort study of 5888 older adults.
We estimated the age- and sex-specific probabilities of transition from one health state to another and from one weight category to another. From these probabilities we estimated future life expectancy, years of healthy life, active life expectancy, and the number of years spent in each weight and health category after age 65.
Women who are healthy and of normal weight at age 65 have a life expectancy of 22.1 years. Of that, they spend, on average, 9.6 years as overweight or obese, and 5.3 years in fair or poor health. For both men and women, being underweight at age 65 was associated with worse outcomes than normal weight, while overweight and obesity were rarely worse than normal weight, and were sometimes associated with significantly better outcomes.
Similar to middle-aged populations, older adults are likely to be or to become overweight or obese. However, higher weight is not associated with worse health in this age group. Thus, the number of older adults at a “healthy” weight may be much higher than currently believed.
self-rated health; equilibrium; activities of daily living; years of healthy life; active life expectancy; multi-state life tables; older adults
Consider a 3-state system with one absorbing state, such as Healthy, Sick, and Dead. Over time, the prevalence of the Healthy state will approach an “equilibrium” value that is independent of the initial conditions. We derived this equilibrium prevalence (Prev:Equil) as a function of the local transition probabilities. We then used Prev:Equil to estimate the expected number of years spent in the healthy state over time. This estimate is similar to one calculated by multi-state life table methods, and has the advantage of having an associated standard error. In longitudinal data for older adults, the standard error was accurate when a valid survival table was known from other sources, or when the available data were sufficient to estimate survival accurately. Performance was better with fewer waves of data. If validated in other situations, these equilibrium estimates of prevalence and years of healthy life (YHL) and their standard errors may be useful when the goal is to compare YHL for different populations.
self-rated health; years of healthy life; prevalence; multi-state lifetable; variance for area under the curve; Sullivan method
To characterize longitudinal patterns of musculoskeletal pain in a community sample of older adults over a 6-year period and to identify factors associated with persistence of pain.
Secondary analysis of the Cardiovascular Health Study.
Community-based cohort drawn from four U.S. counties.
Five thousand ninety-three men and women aged 65 and older.
Over a 6-year period, pain was assessed each year using a single question about the presence of pain in any bones or joints during the last year. If affirmative, participants were queried about pain in seven locations (hands, shoulders, neck, back, hips, knees, feet). Participants were categorized according to the percentage of time that pain was present and according to the intermittent or chronic pattern of pain. Factors associated with persistent pain during five remaining years of the study were identified.
Over 6 years, 32% of participants reported pain for three or more consecutive years, and 32% reported pain intermittently. Of those who reported pain the first year, 54% were pain free at least once during the follow-up period. Most of the pain at specific body locations was intermittent. Factors associated with remission of pain over 5 years included older age, male sex, better self-rated health, not being obese, taking fewer medications, and having fewer depressive symptoms. Approximately half of those with pain reported fewer pain locations the following year.
Musculoskeletal pain in older adults, despite high prevalence, is often intermittent. The findings refute the notion that pain is an inevitable, unremitting, or progressive consequence of aging.
pain; musculoskeletal; longitudinal analysis; remission; persistence; symptoms
To explore the association of major depressive symptoms with advancing age, sex, and self-rated health among older adults.
Design and methods
We analyzed 10 years of annual assessments in a longitudinal cohort of 5888 Medicare recipients in the Cardiovascular Health Study. Self-rated health was assessed with a single question, and subjects categorized as healthy or sick. Major depressive symptoms were assessed using the Center for Epidemiologic Studies Short Depression Scale, with subjects categorized as nondepressed (score < 10) or depressed (≥ 10). Age-, sex-, and health-specific prevalence of depression and the probabilities of transition between depressed and nondepressed states were estimated.
The prevalence of a major depressive state was higher in women, and increased with advancing age. The probability of becoming depressed increased with advancing age among the healthy but not the sick. Women showed a greater probability than men of becoming depressed, regardless of health status. Major depressive symptoms persisted over one-year intervals in about 60% of the healthy and 75% of the sick, with little difference between men and women.
Clinically significant depressive symptoms occur commonly in older adults, especially women, increase with advancing age, are associated with poor self-rated health, and are largely intransigent. In order to limit the deleterious consequences of depression among older adults, increased attention to prevention, screening, and treatment is warranted. A self-rated health item could be used in clinical settings to refine the prognosis of late-life depression.
self-rated health; mental health; epidemiology
To evaluate associations between mid- and late-life obesity and risk of dementia.
Prospective cohort followed 5.4 years from 1992/4 through 1999.
Community-dwelling sample in four US sites recruited from Medicare eligibility files.
2,798 adults without dementia, mean age 74.7 years, 59.1% women, participating in the Cardiovascular Health Cognition Study completing a magnetic resonance image, measured for height and weight at baseline (late-life) and self-reporting weight at age 50 (mid-life). Body mass index (BMI) was calculated at both times.
Main Outcome Measures
Dementia, Alzheimer’s disease (AD) and vascular dementia (VaD) classified by a multidisciplinary committee using standardized criteria.
Classification resulted in 480 persons with incident dementia, 245 with AD (no VaD) and 213 with VaD (with or without AD). In evaluations of mid-life obesity, an increased risk of dementia was found for obese (BMI >30) compared to normal (BMI 20-25) persons adjusted for demographics (HR: 1.39, 95% CI: 1.03-1.87) and for caradiovascularl risk factors (HR: 1.36, 95% CI: 0.94-1.95). The risk estimates reversed in assessments of late-life BMI. Underweight persons (BMI < 20) had an increased risk of dementia (HR: 1.62, 95% CI: 1.02-2.64) while being overweight (BMI 25-30) was not associated (HR: 0.92, 95% CI: 0.72-1.18) and being obese reduced the risk of dementia (HR: 0.63, 95% CI: 0.44-0.91) compared to those with normal BMI.
These results help explain the “obesity paradox” as differences in dementia risk over time are consistent with physical changes in the trajectory toward disability.
The objective of this study was to test if an Automated External Defibrillator (AED) training program would positively affect the mental health of family members of high risk patients.
305 ischemic heart disease patients and their family members were randomized to one of four AED training programs: two video-based training programs and two face-to-face training programs that emphasized self-efficacy and perceived control. Patients and family members were surveyed at baseline, 3 and 9 months post ischemic event on demographic characteristics, measures of quality of life (SF=36) , self-efficacy and perceived control. For this study, family members were the focus rather than the patients.
Regression analyses showed that family members in the face-to-face training programs did not score better on any of the mental health status variables than family members who participated in the other training programs but for an increase in self-efficacy beliefs at 3 months post training.
The findings suggest that a specifically designed AED training program emphasizing self-efficacy and perceived control beliefs is not likely to enhance family member mental health.
Introduction. Successful aging has many dimensions, which may manifest differently in men and women at different ages. Methods. We characterized one-year transitions among health states in 12 measures of successful aging among adults in the Cardiovascular Health Study. The measures included self-rated health, ADLs, IADLs, depression, cognition, timed walk, number of days spent in bed, number of blocks walked, extremity strength, recent hospitalizations, feelings about life as a whole, and life satisfaction. We dichotomized variables into “healthy” or “sick,” states, and estimated the prevalence of the healthy state and the probability of transitioning from one state to another, or dying, during yearly intervals. We compared men and women and three age groups (65–74, 75–84, and 85–94). Findings. Measures of successful aging showed similar results by gender. Most participants remained healthy even into advanced ages, although health declined for all measures. Recuperation, although less common with age, still occurred frequently. Men had a higher death rate than women regardless of health status, and were also more likely to remain in the healthy state. Discussion. The results suggest a qualitatively different experience of successful aging between men and women. Men did not simply “age faster” than women.
Introduction. The traditional definitions of overweight and obesity are not age specific, even though the relationship of weight to mortality is different for older adults. Effects of adiposity on aspects of health beside mortality have not been well investigated. Methods. We calculated the number of years of healthy life (YHL) in the 10 years after baseline, for 5,747 older adults. YHL was defined in 16 different ways. We compared Normal and Overweight persons, classified either by body mass index (BMI) or by waist circumference (WC). Findings. YHL for Normal and Overweight persons differed significantly in 25% of the comparisons, of which half favored the Overweight. Measures of physical health favored Normal weight, while measures of mental health and quality of life favored Overweight. Overweight was less favorable when defined by WC than by BMI. Obese persons usually had worse outcomes. Discussion. Overweight older adults averaged as many years of life and years of healthy life as those of Normal weight. There may be no outcome based reason to distinguish Normal from Overweight for older adults. Conclusion. The “Overweight paradox” appears to hold for nonmortality outcomes. New adiposity standards are needed for older adults, possibly different by race and sex.
To estimate the likelihood of, and factors associated with, recovery from exhaustion in older adults
Design and Setting
Retrospective analysis of data from six annual examinations of a community-based cohort study
4584 men and women aged 69 years or older
Exhaustion was considered present when a participant responded “a moderate amount” or “most of the time” to either of two questions: “How often have you had a hard time getting going?” and “How often does everything seem an effort?”
Of the 964 participants who originally reported exhaustion, 634 (65.8%) were exhaustion-free at least once during follow up. When data from all time points were considered, 48% of exhaustion-reporters were exhaustion-free the following year. After adjustment for age, sex, race, education, and marital status, one-year recovery was less likely among individuals with worse self-rated health, ≥ six medications, obesity, depression, musculoskeletal pain, and history of stroke. In proportional hazards models, the following risk factors were associated with more persistent exhaustion over five years: poor self-rated health, ≥ six medications, obesity, and depression. Recovery was not less likely among participants with a history of cancer or heart disease.
Exhaustion is common in old age but is quite dynamic, even among those with a history of cancer and congestive heart failure. Recovery is especially likely among seniors who have a positive perception of their overall health, take few medications, and are not obese or depressed. These findings support the notion that resiliency is associated with physical and psychological well-being.
symptoms; frailty; fatigue; transition analysis
Older adults are often advised to walk more, but randomized trials have not conclusively established the benefits of walking in this age group. Typical analyses based on observational data may have biased results. Here, we propose a “limited-bias,” more interpretable estimate of the health benefits to sedentary healthy older adults of walking more, using longitudinal data from the Cardiovascular Health Study.
The number of city blocks walked per week, collected annually, was classified as sedentary (<7 blocks per week), somewhat active, or active (≥28). Analysis was restricted to persons sedentary and healthy in the first 2 years. In Year 3, some became more active (the treatment groups). Self-rated health at Year 5 (follow-up) was regressed on walking at Year 3, with additional covariates from Year 2, when all were sedentary.
At follow-up, 83.5% of those active at baseline had excellent, very good, or good self-rated health, as compared with 63.9% of the sedentary, an apparent benefit of 19.6 percentage points. After covariate adjustment, the limited-bias estimate of the benefit was 11.2 percentage points (95% confidence interval 3.7–18.6). Ten different outcome measures showed a benefit, ranging from 5 to 11 percentage points. Estimates from other study designs were smaller, less interpretable, and potentially more biased.
In longitudinal studies where walking and health are ascertained at every wave, limited-bias estimates can provide better estimates of the benefits of walking. A surprisingly small increase in walking was associated with meaningful health benefits.
Exercise; Walking; Selection bias; Self-rated health; ADL
The purpose of this analysis was to compare health care expenditures between insured patients with back pain, fibromyalgia syndrome, or menopause symptoms who used complementary and alternative medical (CAM) providers for some of their care to a matched group of patients who did not use any CAM care. Insurance coverage was equivalent for both conventional and CAM providers.
Insurance claims data for 2000–2003 from Washington State, which mandates coverage of CAM providers, were analyzed. CAM-using patients were matched to CAM-nonusing patients based on age group, gender, index medical condition, overall disease burden, and prior-year expenditures.
Both unadjusted tests and linear regression models indicated that CAM users had lower average expenditures than nonusers. (Unadjusted: $3,797 versus $4,153, p = 0.0001; β from linear regression -$367 for CAM users.) CAM users had higher outpatient expenditures that which were offset by lower inpatient and imaging expenditures. The largest difference was seen in the patients with the heaviest disease burdens among whom CAM users averaged $1,420 less than nonusers, p < 0.0001, which more than offset slightly higher average expenditures of $158 among CAM users with lower disease burdens.
This analysis indicates that among insured patients with back pain, fibromyalgia, and menopause symptoms, after minimizing selection bias by matching patients who use CAM providers to those who do not, those who use CAM will have lower insurance expenditures than those who do not use CAM.
Women with ovarian cancer have reported abdominal/pelvic pain, bloating, difficulty eating or feeling full quickly, and urinary frequency/urgency prior to diagnosis. We explored these findings in a general population using a dataset of insured women aged 40–64 and investigated the potential effectiveness of a routine review of claims data as a prescreen to identify women at high risk for ovarian cancer.
Data from a large Washington State health insurer were merged with the Seattle-Puget Sound Surveillance, Epidemiology and End Results (SEER) cancer registry for 2000–2004. We estimated the prevalence of symptoms in the 36 months prior to diagnosis for early and late-stage ovarian cancer cases and for two comparison groups. The potential performance of a passive screener that would flag women with two or more visits for any of the symptoms in the previous 2-month period was examined.
Of the 223,903 insured women, 161 had incident cases of ovarian cancer. Both early and late-stage patients had a higher prevalence of abdominal/pelvic pain and bloating than the comparison groups, primarily in the 3 months before diagnosis. The passive screener had a sensitivity of 0.31 and specificity of 0.83 and usually identified women right before diagnosis. Assuming an average cost of $500 per false positive, the screener would be considered cost-effective if the true positives had an average increase of 8.5 years of life expectancy.
These results support previous findings that ovarian cancer symptoms were reported in health insurance claims and were more prevalent before diagnosis, but the symptoms may occur too close to the diagnosis date to provide useful diagnostic information. The passive screening approach should be reevaluated in the future using electronic medical records; if found to be effective, the method may be potentially useful for other incident diseases.
Analysis of outcome measures from nonrandomized, observational studies of people participating or not participating in health programs may be suspect because of selection bias. For example, fitness programs may preferentially enroll people who are already committed to healthy lifestyles, including use of preventive services. Some of our earlier studies have attempted to account for this potential bias by including an ad hoc preventive services index created from the patient's number of earlier clinical preventive services, to adjust for health-seeking behaviors. However, this index has not been validated. We formally evaluated the performance of this preventive services index by comparing it with its component parts and with an alternative index derived from principal component analysis by using the weighted sums of the principal components.
We used data from a cohort of 38,046 older adults. We used the following variables from the administrative database of a health maintenance organization to create this index: fecal occult blood test, flexible sigmoidoscopy, screening mammogram, prostate cancer screening, influenza vaccination, pneumococcal vaccination, and preventive care office visits.
The preventive services index was positively correlated with each of the following components: colon cancer screening (r = .752), screening mammogram (r = .559), prostate cancer screening (r = .592), influenza vaccination (r = .844), pneumococcal vaccination (r = .487), and preventive care office visits (r = .737). An alternative preventive services index, created by using principal component analysis, had similar performance.
A preventive services index created by using administrative data has good face validity and construct validity and can be used to partially adjust for selection bias in observational studies of cost and use outcomes.
This article reports findings from a randomized controlled trial of massage and guided meditation with patients at the end of life. Using data from 167 randomized patients, the authors consider patient outcomes through 10 weeks post-enrollment, as well as next-of-kin ratings of the quality of the final week of life for 106 patients who died during study participation. Multiple regression models demonstrated no significant treatment effects of either massage or guided meditation, delivered up to twice a week, when compared with outcomes of an active control group that received visits from hospice-trained volunteers on a schedule similar to that of the active treatment arms. The authors discuss the implications of their findings for integration of these complementary and alternative medicine therapies into standard hospice care.
We used a longitudinal data set covering 13 years from the Cardiovascular Health Study to evaluate the properties of a recently developed approach to deal with left censoring that fits a semi-Markov process (SMP) model by using an analog to the stochastic EM algorithm—the SMP-EM approach. It appears that the SMP-EM approach gives estimates of duration-dependent probabilities of health changes similar to those obtained by using SMP models that have the advantage of actual duration data. SMP-EM estimates of duration-dependent transition probabilities also appear more accurate and less variable than multi-state life table estimates.
multi-state life table; semi-Markov process model; functional disability; healthy aging; event history analysis; left censoring
Self-rated health is an important indicator of future morbidity and mortality. Past research has indicated that self-rated health is related to both levels of and changes in physical functioning. However, no previous study has jointly modeled longitudinal functional status and self-rated health trajectories. We propose a joint model for self-rated health and physical functioning that describes the relationship between perceptions of health and the rate of change of physical functioning or disability. Our joint model uses a non-homogeneous Markov process for discrete physical functioning states and connects this to a logistic regression model for “healthy” versus “unhealthy” self-rated health through parameters of the physical functioning model. We use simulation studies to establish finite sample properties of our estimators and show that this model is robust to misspecification of the functional form of the relationship between self-rated health and rate of change of physical functioning. We also show that our joint model performs better than an empirical model based on observed changes in functional status. We apply our joint model to data from the Cardiovascular Health Study (CHS), a large, multi-center, longitudinal study of older adults. Our analysis indicates that self-rated health is associated both with level of functioning as indicated by difficulty with activities of daily living (ADL) and instrumental activities of daily living (IADL), and the risk of increasing difficulty with ADLs and IADLs.
Disability; functional status; joint modeling; Markov process; non–homogeneous; self–rated health
Diverse analysis approaches have been proposed to distinguish data missing due to death from nonresponse, and to summarize trajectories of longitudinal data truncated by death. We demonstrate how these analysis approaches arise from factorizations of the distribution of longitudinal data and survival information. Models are illustrated using cognitive functioning data for older adults. For unconditional models, deaths do not occur, deaths are independent of the longitudinal response, or the unconditional longitudinal response is averaged over the survival distribution. Unconditional models, such as random effects models fit to unbalanced data, may implicitly impute data beyond the time of death. Fully conditional models stratify the longitudinal response trajectory by time of death. Fully conditional models are effective for describing individual trajectories, in terms of either aging (age, or years from baseline) or dying (years from death). Causal models (principal stratification) as currently applied are fully conditional models, since group differences at one timepoint are described for a cohort that will survive past a later timepoint. Partly conditional models summarize the longitudinal response in the dynamic cohort of survivors. Partly conditional models are serial cross-sectional snapshots of the response, reflecting the average response in survivors at a given timepoint rather than individual trajectories. Joint models of survival and longitudinal response describe the evolving health status of the entire cohort. Researchers using longitudinal data should consider which method of accommodating deaths is consistent with research aims, and use analysis methods accordingly.
Censoring; Generalized estimating equations; Longitudinal data; Missing data; Quality of life; Random effects models; Truncation by death