A reevaluation of the duration of survival after the onset of dementia

Feelings of Hopelessness in Midlife and Cognitive Health in Later Life: A Prospective Population-Based Cohort Study

BACKGROUND

Several studies have found depression and depressive feelings to be associated with subsequent dementia. As dementias typically have a long preclinical development phase, it has been difficult to determine whether depression and depressive feelings reflect a concurrent underlying dementia disease, rather than playing a causative role. Our aim was to investigate hopelessness, one dimension of depressive feelings, and evaluate the likelihood of a prodromal versus a causative role of hopelessness feelings in dementia development.

METHODS

We invited a random sample of 2000 survivors from a representative population in Eastern Finland, originally investigated in midlife between 1972 and 1987, for re-examination an average of 21 years later. The age of the 1449 persons who accepted the invitation was between 39 and 64 years (mean 50.4 years) in midlife and between 65 and 80 (mean 71.3) at follow-up. To measure feelings of hopelessness in midlife and at follow-up, the participants indicated their level of agreement to two statements about their own possible future. We used logistic regression to investigate the association between the combined scores from these two items and cognitive health at follow-up, while adjusting for several health and life-style variables from midlife and for apolipoprotein E4 (ApoE4) status, depression and hopelessness feelings at follow-up. We compared the associations with late-life cognitive health when feelings of hopelessness were either measured in midlife or at the follow-up. In addition we analyzed the changes in hopelessness scores from midlife to follow-up in participants who were either cognitively healthy or impaired at follow-up.

RESULTS

We found higher levels of hopelessness in midlife, but not at follow-up, to be associated with cognitive impairment at follow-up; the adjusted odds ratio for each step of the five-level hopelessness scale was 1.30 (95% confidence interval 1.11-1.51) for any cognitive impairment and 1.37 (1.05-1.78) for Alzheimer's disease. These associations remained significant also after the final adjustments for depressive feelings and for hopelessness at follow-up. The individual changes in hopelessness scores between midlife and follow-up were not systematically related to cognitive health at the follow-up.

CONCLUSION

Our results suggest that feelings of hopelessness already in midlife may have long-term implications for cognitive health and increase the risk of Alzheimer's disease in later life.

Mortality in incident dementia - results from the German Study on Aging, Cognition, and Dementia in Primary Care Patients

OBJECTIVE

Dementia is known to increase mortality, but the relative loss of life years and contributing factors are not well established. Thus, we aimed to investigate mortality in incident dementia from disease onset.

METHOD

Data were derived from the prospective longitudinal German AgeCoDe study. We used proportional hazards models to assess the impact of sociodemographic and health characteristics on mortality after dementia onset, Kaplan-Meier method for median survival times.

RESULTS

Of 3214 subjects at risk, 523 (16.3%) developed incident dementia during a 9-year follow-up period. Median survival time after onset was 3.2 years (95% CI = 2.8-3.7) at a mean age of 85.0 (SD = 4.0) years (≥2.6 life years lost compared with the general German population). Survival was shorter in older age, males other dementias than Alzheimer's, and in the absence of subjective memory complaints (SMC).

CONCLUSION

Our findings emphasize that dementia substantially shortens life expectancy. Future studies should further investigate the potential impact of SMC on mortality in dementia.

Cognition, even in the normal range, predicts disability: cross-sectional and prospective analyses of a population-based sample

OBJECTIVE

To determine if the modified mini-mental state examination (3MS) predicts functional status and if any effect on function is observed within the normal range of cognition.

DESIGN

Cohort study.

SETTING

Community-dwelling older adults in the Canadian province of Manitoba sampled in 1991 and followed in 1996.

PARTICIPANTS

Baseline sample of 1751 adults aged 65+ from a representative registry. Five years later, 1028 participants remained in the community and had no missing data.

MEASUREMENTS

The 3MS, age, gender, education, living arrangements, self-rated health, and depressive symptoms were self-reported. Functional status was assessed using the Older Americans Resource Survey, which was dichotomized into no/mild disability versus moderate/severe disability.

RESULTS

Baseline 3MS score predicted baseline functional status. This effect was a gradient across the entire 3MS score, extending into the normal range with no apparent threshold. In logistic regression models, the unadjusted odds ratio (OR, 95% confidence interval) for the association of 3MS score with disability was 0.94 (0.93, 0.95); the adjusted OR was 0.96 (0.95, 0.98) in models including age, gender, education, and other covariates. Baseline 3MS score also predicted functional status 5 years later: The unadjusted OR for disability was 0.94 (0.92, 0.95); the adjusted OR was 0.97 (0.95, 0.99). Again, the risk of functional impairment at time 2 was a gradient effect, extending into the normal range of baseline 3MS score.

CONCLUSIONS

The 3MS predicts functional decline, and this effect is a gradient effect. These results support the hypothesis that cognition is a continuum in risk.

Prescribing for Australians living with dementia: study protocol using the Delphi technique

INTRODUCTION

Prescribing is complicated for people living with dementia, and careful consideration should be given to continuing and initiating all medicines. This study aims to elicit opinion and gain consensus on appropriate medicine use for people living with dementia in Australia to create a consensus-based list of explicit prescribing criteria.

METHODS AND ANALYSIS

A Delphi technique will be used to develop explicit criteria of medication use in adults aged 65 years and above. An interdisciplinary panel of Australian experts in geriatric therapeutics will be convened that will consist of a minimum of 10 participants. To develop the consensus-based criteria, this study will use an iterative, anonymous, multistaged approach with controlled feedback. Round 1 questionnaire will be administered, and subsequently qualitatively analysed. The round 1 results will be fed back to the panel members, and a round 2 questionnaire developed using questions on a five-point Likert scale. This process will repeat until consensus is developed, or diminishing returns are noted.

ETHICS AND DISSEMINATION

All participants will be provided with a participant information sheet, and sign a written consent form. Ethical approval has been granted from the University of Western Australia's Human Research Ethics Committee (HREC) (reference: RA/4/1/7172). We expect that data from this study will result in a paper published in a peer-reviewed clinical journal and will also present the results at conferences.

The Effects of Anti-Dementia and Nootropic Treatments on the Mortality of Patients with Dementia: A Population-Based Cohort Study in Taiwan

Background

Few studies have examined the contribution of treatment on the mortality of dementia based on a population-based study.

Objective

To investigate the effects of anti-dementia and nootropic treatments on the mortality of dementia using a population-based cohort study.

Methods

12,193 incident dementia patients were found from 2000 to 2010. Their data were compared with 12,193 age- and sex-matched non-dementia controls that were randomly selected from the same database. Dementia was classified into vascular (VaD) and degenerative dementia. Mortality incidence and hazard ratios (HRs) were calculated.

Results

The median survival time was 3.39 years (95% confidence interval [CI]: 2.88–3.79) for VaD without medication, 6.62 years (95% CI: 6.24–7.21) for VaD with nootropics, 3.01 years (95% CI: 2.85–3.21) for degenerative dementia without medication, 8.11 years (95% CI: 6.30–8.55) for degenerative dementia with anti-dementia medication, 6.00 years (95% CI: 5.73–6.17) for degenerative dementia with nootropics, and 9.03 years (95% CI: 8.02–9.87) for degenerative dementia with both anti-dementia and nootropic medications. Compared to the non-dementia group, the HRs among individuals with degenerative dementia were 2.69 (95% CI: 2.55–2.83) without medication, 1.46 (95% CI: 1.39–1.54) with nootropics, 1.05 (95% CI: 0.82–1.34) with anti-dementia medication, and 0.92 (95% CI: 0.80–1.05) with both nootropic and anti-dementia medications. VaD with nootropics had a lower mortality (HR: 1.25, 95% CI: 1.15–1.37) than VaD without medication (HR: 2.46, 95% CI: 2.22–2.72).

Conclusion

Pharmacological treatments have beneficial effects for patients with dementia in prolonging their survival.

Rank-based testing of equal survivorship based on cross-sectional survival data with or without prospective follow-up

Existing linear rank statistics cannot be applied to cross-sectional survival data without follow-up since all subjects are essentially censored. However, partial survival information are available from backward recurrence times and are frequently collected from health surveys without prospective follow-up. Under length-biased sampling, a class of linear rank statistics is proposed based only on backward recurrence times without any prospective follow-up. When follow-up data are available, the proposed rank statistic and a conventional rank statistic that utilizes follow-up information from the same sample are shown to be asymptotically independent. We discuss four ways to combine these two statistics when follow-up is present. Simulations show that all combined statistics have substantially improved power compared with conventional rank statistics, and a Mantel-Haenszel test performed the best among the proposal statistics. The method is applied to a cross-sectional health survey without follow-up and a study of Alzheimer's disease with prospective follow-up.

Double bias: estimation of causal effects from length-biased samples in the presence of confounding

Length bias in survival data occurs in observational studies when, for example, subjects with shorter lifetimes are less likely to be present in the recorded data. In this paper, we consider estimating the causal exposure (treatment) effect on survival time from observational data when, in addition to the lack of randomization and consequent potential for confounding, the data constitute a length-biased sample; we hence term this a double-bias problem. We develop estimating equations that can be used to estimate the causal effect indexing the structural Cox proportional hazard and accelerated failure time models for point exposures in double-bias settings. The approaches rely on propensity score-based adjustments, and we demonstrate that estimation of the propensity score must be adjusted to acknowledge the length-biased sampling. Large sample properties of the estimators are established and their small sample behavior is studied using simulations. We apply the proposed methods to a set of, partly synthesized, length-biased survival data collected as part of the Canadian Study of Health and Aging (CSHA) to compare survival of subjects with dementia among institutionalized patients versus those recruited from the community and depict their adjusted survival curves.

Semiparametric likelihood inference for left-truncated and right-censored data

This paper proposes a new estimation procedure for the survival time distribution with left-truncated and right-censored data, where the distribution of the truncation time is known up to a finite-dimensional parameter vector. The paper expands on the Vardis multiplicative censoring model (Vardi, 1989. Multiplicative censoring, renewal processes, deconvolution and decreasing density: non-parametric estimation. Biometrika 76: , 751-761), establishes the connection between the likelihood under a generalized multiplicative censoring model and that for left-truncated and right-censored survival time data, and derives an Expectation-Maximization algorithm for model estimation. A formal test for checking the truncation time distribution is constructed based on the semiparametric likelihood ratio test statistic. In particular, testing the stationarity assumption that the underlying truncation time is uniformly distributed is performed by embedding the null uniform truncation time distribution in a smooth alternative (Neyman, 1937. Smooth test for goodness of fit. Skandinavisk Aktuarietidskrift 20: , 150-199). Asymptotic properties of the proposed estimator are established. Simulations are performed to evaluate the finite-sample performance of the proposed methods. The methods and theories are illustrated by analyzing the Canadian Study of Health and Aging and the Channing House data, where the stationarity assumption with respect to disease incidence holds for the former but not the latter.

Family caregivers' role implementation at different stages of dementia

PURPOSE

The purpose of this study was to explore family caregivers' role-implementation experiences at different stages of dementia.

PATIENTS AND METHODS

For this cross-sectional, exploratory study, 176 dyads of family caregivers and their community-dwelling elderly relatives with dementia were recruited from the neurological clinics of a medical center in Taiwan. The Family Caregiving Inventory was used to assess family caregivers for caregiving activities, role strain, role preparation, and help from others at different stages of care receivers' dementia.

RESULTS

Family caregivers' caregiving activities were related to patients' stages of dementia. For patients with mild dementia, caregivers provided more assistance in transportation and housekeeping. In addition to these two activities, family caregivers of patients with moderate dementia provided more assistance with mobility and protection. For patients with severe dementia, family caregivers provided more assistance with personal care, mobility and protection, transportation, and housekeeping. Overall, family caregivers reported having some preparation to provide care; the most difficult caregiving activity was identified as managing behavioral problems.

CONCLUSION

This study's results provide a knowledge base for designing dementia stage-specific interventions in clinical practice and developing community-based, long-term care systems for families of patients with dementia.

The New Conceptualization of Alzheimer's Disease under the Microscope of Influential Definitions of Disease

BACKGROUND

According to its new conceptualization, Alzheimer's disease (AD) has preclinical and symptomatic phases, and biomarker abnormality justifies the diagnosis of the disease.

METHODS

The conceptual validity of AD is assessed on the basis of the disease definitions of T. Szasz, R.E. Kendell and J.G. Scadding, C. Boorse, K.W.M. Fulford and J.C. Wakefield, as well as of the DSM-5 classification system.

RESULTS

The new AD conceptualization could fit the Szaszian disease definition, provided that AD biomarkers reflected the pathological hallmarks of a singular disease, but it seems that they do not. Moreover, preclinical AD does not yield a biological disadvantage, being a central criterion for justifying the presence of a disease according to the disease definition of Scadding and Kendell. In addition, it remains unclear whether abnormality of biomarkers in elderly people embodies a statistical deviation from normal ageing and a pathological characteristic. Furthermore, not all stages of AD are related to experiences of failure of intentional doing, which is the criterion of the disease definition of Fulford, whilst the Wakefieldian harmful dysfunction and the DSM-5 mental disorder criteria are fulfilled only in the symptomatic phases of the disease course.

DISCUSSION

Our analytical endeavours unveiled weak sides and the fuzzy boundaries of the new conceptualization of AD. Future refinements of the criteria should address them so that the validity of the AD concept is increased.

Score Estimating Equations from Embedded Likelihood Functions under Accelerated Failure Time Model

The semiparametric accelerated failure time (AFT) model is one of the most popular models for analyzing time-to-event outcomes. One appealing feature of the AFT model is that the observed failure time data can be transformed to identically independent distributed random variables without covariate effects. We describe a class of estimating equations based on the score functions for the transformed data, which are derived from the full likelihood function under commonly used semiparametric models such as the proportional hazards or proportional odds model. The methods of estimating regression parameters under the AFT model can be applied to traditional right-censored survival data as well as more complex time-to-event data subject to length-biased sampling. We establish the asymptotic properties and evaluate the small sample performance of the proposed estimators. We illustrate the proposed methods through applications in two examples.

Long-term efficacy and toxicity of cholinesterase inhibitors in the treatment of Alzheimer disease

Though the symptoms of Alzheimer disease go on for years, the phase 3 trials of the cholinesterase inhibitors (ChEIs), the current mainstay of symptomatic pharmacotherapy for this condition, were typically of only 3- to 6-months' duration. We have limited data on long-term (that is, a year or more) therapy with these agents. In this review, we explore the available information on the biological and clinical effects of long-term ChEI therapy, what happens when these agents are discontinued, and examine what others have recommended An individualized approach to deciding on whether to carry on with a ChEI should be taken. If continued, treatment goals should be clarified and patients monitored over time, for both drug-related benefits and adverse effects.

Comprehensive geriatric assessment in the older cancer patient: coming of age in clinical cancer care

Cancer care at the extremes of life, in the young and the old, is characterized by unique issues associated with pediatrics and geriatric medicine, accentuated by the special vulnerabilities of these groups. In response to these needs, the field of pediatric oncology has been well honed to deal with the special problems associated with juvenile cancer patients. While most adult oncologists consider themselves well prepared to deal with older cancer patients, the current expansion of the geriatric population - their variable levels of fitness, frailty and vulnerability, the fact that cancer is primarily a disease of older adults, the significant expansion of agents and approaches to treat cancer, as well as their resultant toxicities and complications - has led to the development of specialized geriatric oncologists. Moreover, the special characteristics and needs of these patients have led to the evolution of new guidelines for evaluation, management and the conduct of research in older patients with cancer.

Cognitive impairment assessed at annual geriatric health examinations predicts mortality among the elderly

OBJECTIVE

To determine whether cognitive impairment assessed at annual geriatric health examinations is associated with increased mortality in the elderly.

METHOD

This cohort study was based on data obtained from the government-sponsored Annual Geriatric Health Examination Program for the elderly in Taipei City between 2006 and 2010. The study sample consisted of 77,541 community-dwelling Taipei citizens aged 65 years or older. The Short Portable Mental Status Questionnaire (SPMSQ) was selected to measure cognitive impairment. Mortality was ascertained by matching cohort IDs with national death files.

RESULTS

There was a dose-response relationship between cognitive impairment and mortality (increased one score of SPMSQ, Hazard ratio [HR]: 1.12, 95% confidence interval [CI]: 1.10-1.14). Relative to no cognitive impairment, the HRs were 1.67 (95% CI: 1.43-1.94), 2.26 (95% CI: 1.90-2.70), and 2.68 (95% CI: 2.25-3.19) for mild, moderate, and severe cognitive impairments, respectively. The causes of death associated with cognitive impairment were circulatory, respiratory, and other causes, but not death from cancer.

CONCLUSION

Cognitive impairment as measured by the SPMSQ is associated with an increased risk for mortality. Even mild cognitive impairment was associated with greater risk of mortality at a relatively short follow-up time.

Adjuvant systemic treatment for elderly breast cancer patients; addressing safety concerns

INTRODUCTION

The issue of systemic treatment for early breast cancer in the elderly has always been challenging and in spite of the clear evidence of the potential benefits of adjuvant treatment in older women, they are usually undertreated with the potential consequence of worse outcomes.

AREAS COVERED

This article will review the evidence surrounding the various systemic options in the treatment armamentarium of early-stage breast cancer in elderly patients. The risks and benefits, with particular attention to a number of newly introduced targeted agents, along with the potential role of incorporating a combined geriatric/oncologic assessment as a routine part of the management of elderly patients with breast cancer are considered.

EXPERT OPINION

Administration of available options for (neo)adjuvant endocrine, chemo, as well as targeted therapeutics in fit elderly patients is feasible and tolerable; however, a routine input from geriatric medicine and psycho-oncology experts as well as the training of specialized oncology staff with special interest in geriatric oncology are believed to improve the outcome of elderly patients.

Mini-mental state examination as a predictor of mortality among older people referred to secondary mental healthcare

Background

Lower levels of cognitive function have been found to be associated with higher mortality in older people, particularly in dementia, but the association in people with other mental disorders is still inconclusive.

Methods and Findings

Data were analysed from a large mental health case register serving a geographic catchment of 1.23 million residents, and associations were investigated between cognitive function measured by the Mini-Mental State Examination (MMSE) and survival in patients aged 65 years old and over. Cox regressions were carried out, adjusting for age, gender, psychiatric diagnosis, ethnicity, marital status, and area-level socioeconomic index. A total of 6,704 subjects were involved, including 3,368 of them having a dementia diagnosis and 3,336 of them with depression or other diagnoses. Descriptive outcomes by Kaplan-Meier curves showed significant differences between those with normal and impaired cognitive function (MMSE score<25), regardless of a dementia diagnosis. As a whole, the group with lower cognitive function had an adjusted hazard ratio (HR) of 1.42 (95% CI: 1.28, 1.58) regardless of diagnosis. An HR of 1.23 (95% CI: 1.18, 1.28) per quintile increment of MMSE was also estimated after confounding control. A linear trend of MMSE in quintiles was observed for the subgroups of dementia and other non-dementia diagnoses (both p-values<0.001). However, a threshold effect of MMSE score under 20 was found for the specific diagnosis subgroups of depression.

Conclusion

Current study identified an association between cognitive impairment and increased mortality in older people using secondary mental health services regardless of a dementia diagnosis. Causal pathways between this exposure and outcome (for example, suboptimal healthcare) need further investigation.

The natural history of dementia

This review summarizes studies on the natural history of dementia with a focus on Alzheimer's disease and vascular dementia. Understanding the course of dementia is important not only for patients, caregivers, and health professionals, but also for health policy-makers, who have to plan for national resources needed in the management of an increasing number of dementia cases. From the available published data, the life expectancy of elderly people with dementia is shorter than that of non-demented elderly. Reports on survival after a diagnosis of dementia vary from 3 to 12 years. The wide variation is partly due to the diagnostic criteria used in the studies and the sites where they were conducted (i.e. hospitals, clinics, or homes). There is an apparent difference in survival between Alzheimer's disease patients with onset of illness before 75 years and those after 75 years: the younger patients have a longer life expectancy. However, there are conflicting data on survival (in years) comparing male and female patients and comparing patients of different ethnicities. For vascular dementia, published papers on life expectancy vary between 3 to 5 years. Vascular dementia appears to have a poorer prognosis than Alzheimer's disease. The stages of severity of dementia were compared in a follow-up of a sample of Alzheimer's disease patients in Singapore, and the mean duration of the mild phase (clinical dementia rating 1) was 5.6 years, the moderate phase (clinical dementia rating 2) was 3.5 years, and the severe phase (clinical dementia rating 3) was 3.2 years. At the various phases of the disease, the demand on health-care services and economic cost are different.

Propensity Score Estimation in the Presence of Length-biased Sampling: A Nonparametric Adjustment Approach

The pervasive use of prevalent cohort studies on disease duration increasingly calls for an appropriate methodology to account for the biases that invariably accompany samples formed by such data. It is well-known, for example, that subjects with shorter lifetime are less likely to be present in such studies. Moreover, certain covariate values could be preferentially selected into the sample, being linked to the long-term survivors. The existing methodology for estimating the propensity score using data collected on prevalent cases requires the correct conditional survival/hazard function given the treatment and covariates. This requirement can be alleviated if the disease under study has stationary incidence, the so-called stationarity assumption. We propose a nonparametric adjustment technique based on a weighted estimating equation for estimating the propensity score which does not require modeling the conditional survival/hazard function when the stationarity assumption holds. The estimator's large-sample properties are established and its small-sample behavior is studied via simulation. The estimated propensity score is utilized to estimate the survival curves.

Reversal of English trend towards hospital death in dementia: a population-based study of place of death and associated individual and regional factors, 2001-2010

Background

England has one of the highest rates of hospital death in dementia in Europe. How this has changed over time is unknown. This study aimed to analyse temporal trends in place of death in dementia over a recent ten year period.

Methods

Population-based study linking Office for National Statistics mortality data with regional variables, in England 2001–2010. Participants were adults aged over 60 with a death certificate mention of dementia. Multivariable Poisson regression was used to determine the proportion ratio (PR) for death in care home (1) and home/hospice (1) compared to hospital (0). Explanatory variables included individual factors (age, gender, marital status, underlying cause of death), and regional variables derived at area level (deprivation, care home bed provision, urbanisation).

Results

388,899 deaths were included. Most people died in care homes (55.3%) or hospitals (39.6%). A pattern of increasing hospital deaths reversed in 2006, with a subsequent decrease in hospital deaths (−0.93% per year, 95% CI −1.08 to −0.79 p < 0.001), and an increase in care home deaths (0.60% per year, 95% CI 0.45 to 0.75 p < 0.001). Care home death was more likely with older age (PR 1.11, 1.10 to 1.13), and in areas with greater care home bed provision (PR 1.82, 1.79 to 1.85) and affluence (PR 1.29, 1.26 to 1.31). Few patients died at home (4.8%) or hospice (0.3%). Home/hospice death was more likely in affluent areas (PR 1.23, 1.18 to 1.29), for women (PR 1.61, 1.56 to 1.65), and for those with cancer as underlying cause of death (PR 1.84, 1.77 to 1.91), and less likely in the unmarried (PRs 0.51 to 0.66).

Conclusions

Two in five people with dementia die in hospital. However, the trend towards increasing hospital deaths has reversed, and care home bed provision is key to sustain this. Home and hospice deaths are rare. Initiatives which aim to support the end of life preferences for people with dementia should be investigated.

Contribution of Alzheimer disease to mortality in the United States

OBJECTIVE

To assess the burden of mortality attributable to Alzheimer disease (AD) dementia in the United States.

METHODS

Data came from 2,566 persons aged 65 years and older (mean 78.1 years) without dementia at baseline from 2 cohort studies of aging with identical annual diagnostic assessments of dementia. Because both studies require organ donation, ascertainment of mortality was complete and dates of death accurate. Mortality hazard ratios (HRs) after incident AD dementia were estimated per 10-year age strata from proportional hazards models. Population attributable risk percentage was derived to estimate excess mortality after a diagnosis of AD dementia. The number of excess deaths attributable to AD dementia in the United States was then estimated.

RESULTS

Over an average of 8 years, 559 participants (21.8%) without dementia at baseline developed AD dementia and 1,090 (42.4%) died. Median time from AD dementia diagnosis to death was 3.8 years. The mortality HR for AD dementia was 4.30 (confidence interval = 3.33, 5.58) for ages 75-84 years and 2.77 (confidence interval = 2.37, 3.23) for ages 85 years and older (too few deaths after AD dementia in ages 65-74 were available to estimate HR). Population attributable risk percentage was 37.0% for ages 75-84 and 35.8% for ages 85 and older. An estimated 503,400 deaths in Americans aged 75 years and older were attributable to AD dementia in 2010.

CONCLUSIONS

A larger number of deaths are attributable to AD dementia in the United States each year than the number (<84,000 in 2010) reported on death certificates.

Estimating the lifetime risk of dementia in the Canadian elderly population using cross-sectional cohort survival data

Dementia is one of the world's major public health challenges. The lifetime risk of dementia is the proportion of individuals who ever develop dementia during their lifetime. Despite its importance to epidemiologists and policy-makers, this measure does not seem to have been estimated in the Canadian population. Data from a birth cohort study of dementia are not available. Instead, we must rely on data from the Canadian Study of Heath and Aging, a large cross-sectional study of dementia with follow-up for survival. These data present challenges because they include substantial loss to follow-up and are not representatively drawn from the target population because of structural sampling biases. A first bias is imparted by the cross-sectional sampling scheme, while a second bias is a result of stratified sampling. Estimation of the lifetime risk and related quantities in the presence of these biases has not been previously addressed in the literature. We develop and study nonparametric estimators of the lifetime risk, the remaining lifetime risk and cumulative risk at specific ages, accounting for these complexities. In particular, we reveal the fact that estimation of the lifetime risk is invariant to stratification by current age at sampling. We present simulation results validating our methodology, and provide novel facts about the epidemiology of dementia in Canada using data from the Canadian Study of Health and Aging.

Prescribing statins for cardiovascular disease prevention in the old: an absence of evidence and an absence of guidelines

Australia's oldest old are potentially being harmed by the under- and over- use of statins. Variations in prescription of statins are in part due to the vacuum of clinical research trial evidence and paucity of contemporary guidelines that are needed to address the use of lipid lowering therapy in the oldest old. There are a few randomised placebo-controlled trials that recruited an older population. Therefore evidence of statins efficacy in the oldest old is based on an extrapolation of results from those studies. The extensive exclusion criteria of those studies, the relative youth of the study participants, the low levels of comorbidity and functional impairment limit the external validity and the generalisability of the findings. Current guidelines are silent or generally non-specific about statin therapy for the oldest old deferring decisions to individual medical practitioners. Life expectancy, time to benefit, functional status and medication related adverse events, polypharmacy, adherence to treatment are factors that need to be considered when forming appropriate guidelines for statin prescription in the very old. Well-designed clinical trials that account for the heterogeneity of this population are needed. While waiting for this research evidence better clinical guidelines are needed to address this issue.

The impact of arterial stiffness on cognitive status in elderly diabetic patients

With age, arteries become more rigid and pulse waves propagate faster. The pathogenic mechanisms that causes vascular stiffness in type 2 diabetes are complex but incompletely understood. An important element in the development of this phenomenon appears to be insulin resistance. One of the first line health problems that persist in the present is the failure to detect cardiovascular diseases in the preclinical stage which is important since more frequent cardiac events (myocardial infarction, sudden death) occur in people without obvious cardiovascular pathology in the medical history. One of the degenerative diseases with the greatest impact on the autonomy is dementia of elderly people. Recent studies have shown the association and even the possible involvement of cardiovascular risk factors and arterial stiffness in the pathogenesis of dementia and cognitive impairment. Although pulse wave velocity in the aorta is related to subclinical coronary atherosclerosis (being an important biomarker of cardiovascular risk in asymptomatic individuals), arterial stiffness is also a predictor of cognitive performance, cognitive decline or dementia.

Diabetes mellitus and the risk of Alzheimer's disease: a nationwide population-based study

OBJECTIVES

Possible association between diabetes mellitus (DM) and Alzheimer's disease (AD) has been controversial. This study used a nationwide population-based dataset to investigate the relationship between DM and subsequent AD incidence.

METHODS

Data were collected from Taiwan's National Health Insurance Research Database, which released a cohort dataset of 1,000,000 randomly sampled people and confirmed it to be representative of the Taiwanese population. We identified 71,433 patients newly diagnosed with diabetes (age 58.74 ± 14.02 years) since January 1997. Using propensity score, we matched them with 71,311 non-diabetic subjects by time of enrollment, age, gender, hypertension, hyperlipidemia, and previous stroke history. All the patients were followed up to December 31, 2007. The endpoint of the study was occurrence of AD.

RESULTS

Over a maximum 11 years of follow-up, diabetic patients experienced a higher incidence of AD than non-diabetic subjects (0.48% vs. 0.37%, p<0.001). After Cox proportional hazard regression model analysis, DM (hazard ratio [HR], 1.76; 95% confidence interval [CI], 1.50-2.07, p<0.001), age (HR, 1.11; 95% CI, 1.10-1.12, p<0.001), female gender (HR, 1.24; 95% CI, 1.06-1.46, p=0.008), hypertension (HR, 1.30; 95% CI, 1.07-1.59, p=0.01), previous stroke history (HR, 1.79; 95% CI, 1.28-2.50, p<0.001), and urbanization status (metropolis, HR, 1.32; 95% CI, 1.07-1.63, p=0.009) were independently associated with the increased risk of AD. Neither monotherapy nor combination therapy with oral antidiabetic medications were associated with the risk of AD after adjusting for underlying risk factors and the duration of DM since diagnosis. However, combination therapy with insulin was found to be associated with greater risk of AD (HR, 2.17; 95% CI, 1.04-4.52, p=0.039).

CONCLUSION

Newly diagnosed DM was associated with increased risk of AD. Use of hypoglycemic agents did not ameliorate the risk.

Impact of high risk drug use on hospitalization and mortality in older people with and without Alzheimer's disease: a national population cohort study

BACKGROUND

Evidence is lacking about outcomes associated with the cumulative use of anticholinergic and sedative drugs in people with Alzheimer's disease (AD). This retrospective cohort study investigated the relationship between cumulative exposure to anticholinergic and sedative drugs and hospitalization and mortality in people with and without AD in Finland.

METHODS

Community-dwelling people aged 65 years and over, with AD on December 31(st) 2005 (n = 16,603) and individually matched (n = 16,603) comparison persons (age, sex, region of residence) were identified by the Social Insurance Institution of Finland. Drug utilization data were extracted from the Finnish National Prescription Register. Exposure to anticholinergic and sedative drugs was defined using the Drug Burden Index (DBI). Hospitalization and mortality data were extracted from national registers. Cox and zero-inflated negative binomial analyses were used to investigate the relationship between DBI and hospitalization and mortality over a one-year follow-up.

RESULTS

In total, 5.8% of people with AD and 3.7% without AD died during 2006. For every unit increase in DBI, the adjusted hazard ratio for mortality was 1.21 (95% confidence intervals [CI]: 1.09-1.33) among people with AD, and 1.37 (95%CI: 1.20-1.56) among people without AD. Overall, 44.3% of people with AD and 33.4% without AD were hospitalized. When using no DBI exposure as the reference group, the adjusted incidence rate ratio for length of hospital stay among high DBI group (≥1) in people with AD was 1.15 (95%CI: 1.05-1.26) and 1.63 (95%CI: 1.41-1.88) in people without AD.

CONCLUSION

There is a dose-response relationship between cumulative anticholinergic and sedative drug use and hospitalization and mortality in people with and without AD.

An overview of the LASER-AD study: a longitudinal epidemiological study of people with Alzheimer's disease

Research into the epidemiological, clinical characteristics and economic impact of dementia is critical to increase understanding and better inform care and policy, and empower people with Alzheimer's disease (AD) and their families to make preparations and timely decisions about accommodation, care and treatment. The LASER-AD longitudinal study of people with AD and their carers has contributed to our understanding of the progression, characteristics and costs of the disease, and to developing tools that help detect dementia earlier, and screen and identify problems experienced by carers. Our work on quality of life shows that even those with severe dementia can report this meaningfully, although family proxy ratings of quality of life do not necessarily mirror the views of the individual. Despite the impact of the disease process, people with AD experience well-being in adversity and still live fulfilling lives. The study highlights the high prevalence and severity of neuropsychiatric symptoms, carer anxiety, depression and abusive behaviour. It informs future directions for possible interventions, in particular the central role of carer coping strategies in predicting carer mental illness. Current research is building on our findings, which have also been used to inform national and international plans for managing people with dementia and their carers.

GATA2 deficiency: a protean disorder of hematopoiesis, lymphatics, and immunity

Haploinsufficiency of the hematopoietic transcription factor GATA2 underlies monocytopenia and mycobacterial infections; dendritic cell, monocyte, B, and natural killer (NK) lymphoid deficiency; familial myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML); and Emberger syndrome (primary lymphedema with MDS). A comprehensive examination of the clinical features of GATA2 deficiency is currently lacking. We reviewed the medical records of 57 patients with GATA2 deficiency evaluated at the National Institutes of Health from January 1, 1992, to March 1, 2013, and categorized mutations as missense, null, or regulatory to identify genotype-phenotype associations. We identified a broad spectrum of disease: hematologic (MDS 84%, AML 14%, chronic myelomonocytic leukemia 8%), infectious (severe viral 70%, disseminated mycobacterial 53%, and invasive fungal infections 16%), pulmonary (diffusion 79% and ventilatory defects 63%, pulmonary alveolar proteinosis 18%, pulmonary arterial hypertension 9%), dermatologic (warts 53%, panniculitis 30%), neoplastic (human papillomavirus+ tumors 35%, Epstein-Barr virus+ tumors 4%), vascular/lymphatic (venous thrombosis 25%, lymphedema 11%), sensorineural hearing loss 76%, miscarriage 33%, and hypothyroidism 14%. Viral infections and lymphedema were more common in individuals with null mutations (P = .038 and P = .006, respectively). Monocytopenia, B, NK, and CD4 lymphocytopenia correlated with the presence of disease (P < .001). GATA2 deficiency unites susceptibility to MDS/AML, immunodeficiency, pulmonary disease, and vascular/lymphatic dysfunction. Early genetic diagnosis is critical to direct clinical management, preventive care, and family screening.

Survival in dementia and predictors of mortality: a review

OBJECTIVE

Dementia is an important cause of mortality and, with the ageing population and increasing prevalence of dementia, reliable data on prognosis and survival will be of interest to patients and caregivers as well as providers and commissioners of health and social care. A review of the literature was undertaken to determine the rates of survival in dementia and Alzheimer's disease (AD) and to identify factors that are or are not predictive of mortality in dementia and AD.

METHODS

Relevant articles on mortality in dementia were identified following a search of several electronic databases from 1990 to September 2012. Inclusion criteria were reports on prospective community or clinic based cohorts published in English since 1990, to reflect more recent recognition of possible predictors.

RESULTS

Median survival time from age of onset of dementia ranges from 3.3 to 11.7 years, with most studies in the 7 to 10-year period. Median survival time from age of disease diagnosis ranges from 3.2 to 6.6 years for dementia or AD cohorts as a whole. Age was consistently reported as a predictor of mortality, with male gender a less consistent predictor. Increased disease severity and functional impairment were often associated with mortality.

CONCLUSIONS

Substantial heterogeneity in the design of included studies limits the ability to prognosticate for individual patients. However, it is clear that dementia and AD are associated with significant mortality. Reasons for the increased mortality are not established.

Survival of Alzheimer's disease patients in Korea

BACKGROUND/AIMS

The natural history of Alzheimer's disease (AD) has rarely been studied in the Korean population. Our study on survival analyses in Korean AD patients potentially provides a basis for cross-cultural comparisons.

METHODS

We studied 724 consecutive patients from a memory disorder clinic in a tertiary hospital in Seoul, who were diagnosed as having AD between April 1995 and December 2005. Deaths were identified by the Statistics Korea database. The Kaplan-Meier method was used for survival analysis, and a Cox proportional hazard model was used to assess factors related to patient survival.

RESULTS

The overall median survival from the onset of first symptoms and from the time of diagnosis was 12.6 years (95% confidence interval 11.7-13.4) and 9.3 years (95% confidence interval 8.7-9.9), respectively. The age of onset, male gender, history of diabetes mellitus, lower Mini-Mental State Examination score, and higher Clinical Dementia Rating score were negatively associated with survival. There was a reversal of risk of AD between early-onset and later-onset AD, 9.1 years after onset.

CONCLUSIONS

The results of our study show a different pattern of survival compared to those studies carried out with western AD populations. Mortality risk of early-onset AD varied depending on the duration of follow-up.

Predicting the risk of dementia among Canadian seniors: a useable practice-friendly diagnostic algorithm

Research has not provided feasible models to identify dementia in primary care. We construct a broadly based diagnostic algorithm synthesizing information from known risk factors, such as poor cognition, sociodemographic factors, and health history. Data were from the Canadian Study of Health and Aging (CSHA) Phase I. Dementia was diagnosed by clinical consensus. All subjects had a Mini-Mental State Examination (MMSE) score and a Modified MMSE (3MS) score. Multiple logistic regression was used to build our diagnostic algorithm, which was then tested for classification accuracy on the basis of the area under the receiver operating characteristic curve. The area under receiver operating characteristic curve for our diagnostic algorithm using 3MS as a binary variable was significantly greater than the 3MS alone (P<0.001). However, no significant difference was found when using 3MS as a continuous variable in the algorithm. Similarly, a binary MMSE algorithm would provide greater accuracy than MMSE alone. In terms of the usage of our algorithm in practice settings, given the prevalence of dementia, the clear benefits of accurate identification and earlier intervention, adding a few questions to the binary 3MS in our algorithm quantitatively improves the dementia prediction, which is important for patients, caregivers, and health providers.

Cardiac device complications in the cognitively impaired

BACKGROUND

Patients with preexisting mild cognitive impairment or dementia may be at increased risk for developing cardiac device complications due to an impaired ability to follow postimplant care instructions. We sought to determine whether rates of infection, lead dislodgement, or appropriate or inappropriate implantable cardioverter defibrillator (ICD) shocks are increased in this population.

METHODS

Medical charts of 561 patients with mild cognitive impairment or dementia who underwent pacemaker (PM) or ICD implantation between January 2002 and October 2009 at Mayo Clinic were identified. A total of 134 patients who were diagnosed with cognitive impairment or dementia before device implantation or within 1 year of implantation were compared with 134 matched controls. Information was collected on patient characteristics, comorbid medical conditions, ejection fraction, complications, device type, device therapy, and mortality. Device information was prospectively entered into a database and retrospectively reviewed.

RESULTS

Of the 134 patients with mild cognitive impairment and dementia, 99 underwent PM implantation and 35 underwent ICD implantation. Compared to controls, there was no difference in patient characteristics, ejection fraction, or comorbidities except for diabetes, which was more prevalent in the cognitively impaired and demented group (18.7% vs 30.6%, P = 0.02). There was no difference in device therapy and complications (14.4% vs 5.8%, P = 0.268). However, there was a decreased survival in patients with cognitive impairment and dementia when compared to the control group (42% vs 67% at 5 years, P = 0.007).

CONCLUSION

Patients with cognitive impairment and standard device indications are not at increased risk for device complications and therapy but their survival is much lower than in matched controls. The cause of this lower survival is unknown but may be related to the underlying neurological disease. Presence of cognitive impairment should therefore be considered when contemplating implantation of a cardiac device.

Empirical likelihood-based confidence intervals for length-biased data

Logistic or other constraints often preclude the possibility of conducting incident cohort studies. A feasible alternative in such cases is to conduct a cross-sectional prevalent cohort study for which we recruit prevalent cases, that is, subjects who have already experienced the initiating event, say the onset of a disease. When the interest lies in estimating the lifespan between the initiating event and a terminating event, say death for instance, such subjects may be followed prospectively until the terminating event or loss to follow-up, whichever happens first. It is well known that prevalent cases have, on average, longer lifespans. As such, they do not constitute a representative random sample from the target population; they comprise a biased sample. If the initiating events are generated from a stationary Poisson process, the so-called stationarity assumption, this bias is called length bias. The current literature on length-biased sampling lacks a simple method for estimating the margin of errors of commonly used summary statistics. We fill this gap by using the empirical likelihood-based confidence intervals by adapting this method to right-censored length-biased survival data. Both large and small sample behaviors of these confidence intervals are studied. We illustrate our method by using a set of data on survival with dementia, collected as part of the Canadian Study of Health and Aging.

Qualitative evaluation of advanced care planning in early dementia (ACP-ED)

BACKGROUND

End-of-life-care is often poor in individuals with dementia. Advanced care planning (ACP) has the potential to improve end-of-life care in dementia. Commonly ACP is completed in the last six months of life but in dementia there may be problems with this as decision-making capacity and ability to communicate necessarily decrease as the disease progresses. Choosing the right time to discuss ACP with people with dementia may be challenging given the duration of the illness may be up to nine years.

AIMS

To explore the acceptability of discussing ACP with people with memory problems and mild dementia shortly after diagnosis.

METHODS

In-depth interviews were conducted with 12 patients and eight carers who had participated in ACP discussions and six staff members from a memory clinic and a community mental health team who had either conducted or attended the discussions for training purposes.

RESULTS

Patients and carers found ACP a positive intervention that helped them think about the future, enabled people with dementia to make their wishes known, and resulted in their feeling relieved and less worried about the future. The importance of sharing the ACP documentation between health service providers was highlighted.

CONCLUSIONS

This qualitative evaluation of ACP in early dementia has encouragingly positive results which support the wider application of the intervention in memory services and community mental health teams. Strategies are suggested to support the implementation of ACP further in clinical practice.

Survival analysis without survival data: connecting length-biased and case-control data

We show that relative mean survival parameters of a semiparametric log-linear model can be estimated using covariate data from an incident sample and a prevalent sample, even when there is no prospective follow-up to collect any survival data. Estimation is based on an induced semiparametric density ratio model for covariates from the two samples, and it shares the same structure as for a logistic regression model for case-control data. Likelihood inference coincides with well-established methods for case-control data. We show two further related results. First, estimation of interaction parameters in a survival model can be performed using covariate information only from a prevalent sample, analogous to a case-only analysis. Furthermore, propensity score and conditional exposure effect parameters on survival can be estimated using only covariate data collected from incident and prevalent samples.

Mini-Mental Status Examination as predictors of mortality in the elderly

OBJECTIVE

Because the number of elderly is increasing worldwide, cognitive dysfunction becomes important health care issue. This study investigated the association between cognitive dysfunction and mortality in the elderly.

METHOD

Data were analyzed from a longitudinal mortality follow-up study of 2712 Korean elderly aged 60 and over, examined in 2002 with complete data followed an average 6.03 years. Measurements included socio-demographic and clinical factors and Mini-Mental State Examination (MMSE). MMSE was categorized into groups with no, mild, or moderate cognitive dysfunction, and the subscores of MMSE domains were categorized into no dysfunction or dysfunction. The Cox proportional hazards models were conducted to examine the association between MMSE score and mortality, after adjusting for age, gender, education and other socio-demographic factors.

RESULTS

Death during follow-up occurred in 318 subjects. The mortality risk was significantly associated with the elderly with mild cognitive dysfunction [hazard ratio (HR) = 1.93] and with moderate cognitive dysfunction (HR = 2.66). 'Orientation-to-time' (HR = 1.39) and 'Attention' (HR = 1.48) domains of MMSE were independently associated with mortality.

CONCLUSION

This study showed that cognitive dysfunction independently predicted mortality in the elderly. Cognitive dysfunction should be considered part of identifying the elderly at high risk for mortality.

A simple score to predict survival with dementia in the general population

BACKGROUND/AIMS

This study was designed to develop a practical risk score for predicting 5-year survival after the diagnosis of dementia.

METHODS

Using the Paquid Study (prospective, population-based, long-term cohort study), we created a prognosis score with incident cases of dementia and validated it in another prospective, population-based, long-term cohort study, the Three City Study. -

RESULTS

Among the 3,777 subjects enrolled in the Paquid Study, 454 incident cases of dementia were included in this study. After a 5-year follow-up period, 319 (70.3%) were deceased. The score was constructed from three independent prognostic variables (gender, age at diagnosis and number of ADL restricted). The discriminant ability of the score was good with a c index of 0.754. Sensitivity was 64.7% and specificity 76.3%. In the validation cohort, the discriminant ability of the prognostic score with c statistics was 0.700. Sensitivity was 26.3% and specificity 95.4%.

CONCLUSIONS

The prognostic factors selected in the predictive model are easily assessable, so this simple score could provide helpful information for the management of dementia, particularly to identify patients with duration of the disease greater than 5 years.

Regression with incomplete covariates and left-truncated time-to-event data

Studies of chronic diseases routinely sample individuals subject to conditions on an event time of interest. In epidemiology, for example, prevalent cohort studies aiming to evaluate risk factors for survival following onset of dementia require subjects to have survived to the point of screening. In clinical trials designed to assess the effect of experimental cancer treatments on survival, patients are required to survive from the time of cancer diagnosis to recruitment. Such conditions yield samples featuring left-truncated event time distributions. Incomplete covariate data often arise in such settings, but standard methods do not deal with the fact that individuals' covariate distributions are also affected by left truncation. We describe an expectation-maximization algorithm for dealing with incomplete covariate data in such settings, which uses the covariate distribution conditional on the selection criterion. We describe an extension to deal with subgroup analyses in clinical trials for the case in which the stratification variable is incompletely observed.

Longitudinal Changes in the Government-Certified Index Stage and Requisite Costs for Long-Term Care Insurance System among the Community-Dwelling Demented Elderly in Japan

Background. A new public long-term care (LTC) insurance was launched in 2000 in Japan. However, there have been few studies involving factors that increase LTC costs of demented subjects; no follow-up studies involving the Government-Certified Index (GCI) and requisite costs related to the causes of dementia. Method. An epidemiological survey was conducted in a rural area in Japan in 1999, and 271 subjects were diagnosed as dementia patients. Age, sex, mini-mental state examination, clinical dementia rating, activity of daily living, causes of dementia, and coexisting physical disease were confirmed. After the LTC insurance has been launched, we tracked the GCI stages and payment amounts every month for 8 years. Result. 209 subjects were certified to be eligible for LTC insurance; however, 13 did not receive any payment. Only 49 out of 209 were alive after the follow-up period. The most common cause of dementia was Alzheimer's disease (AD), followed by vascular dementia (VaD). There was no significant difference between the mortality rates of the two groups. VaD subjects required higher costs than AD subjects in the total certified period and in GCI stage 5. Conclusion. Our results indicate that causes of dementia can have an impact on the requisite costs for the LTC insurance.

Semiparametric estimation for the additive hazards model with left-truncated and right-censored data

Survival data from prevalent cases collected under a cross-sectional sampling scheme are subject to left-truncation. When fitting an additive hazards model to left-truncated data, the conditional estimating equation method (Lin & Ying, 1994), obtained by modifying the risk sets to account for left-truncation, can be very inefficient, as the marginal likelihood of the truncation times is not used in the estimation procedure. In this paper, we use a pairwise pseudolikelihood to eliminate nuisance parameters from the marginal likelihood and, by combining the marginal pairwise pseudo-score function and the conditional estimating function, propose an efficient estimator for the additive hazards model. The proposed estimator is shown to be consistent and asymptotically normally distributed with a sandwich-type covariance matrix that can be consistently estimated. Simulation studies show that the proposed estimator is more efficient than its competitors. A data analysis illustrates application of the method.

Time-dependent study entries and exposures in cohort studies can easily be sources of different and avoidable types of bias

OBJECTIVES

To display and discuss the reasons and consequences of length and time-dependent bias. They might occur in presence of a time-dependent study entry or a time-dependent exposure which might change from unexposed to exposed.

STUDY DESIGN AND SETTING

Recalling the popular study of Oscar nominees and using a real-data example from hospital epidemiology, we give innovative and easy-to-understand graphical presentations of how these biases corrupt the analyses via distorted time-at-risk. Cumulative hazard plots and Cox proportional hazards models were used. We are building bridges to medical disciplines such as critical care medicine, hepatology, pharmaco-epidemiology, transplantation medicine, neurology, gynecology and cardiology.

RESULTS

In presence of time-dependent bias, the hazard ratio (comparing exposed with unexposed) is artificially underestimated. The length bias leads to an artificial underestimation of the overall hazard. When both biases coexist it can lead to different directions of biased hazard ratios.

CONCLUSION

Since length and time-dependent bias might occur in several medical disciplines, we conclude that understanding and awareness are the best prevention of survival bias.

Modeling cost-effectiveness of pharmaceuticals in Alzheimer's disease

Alzheimer's disease is a neurodegenerative disorder characterized by cognitive and behavioral deficits. Donepezil and memantine are two medications used to treat the symptoms of cognitive decline in Alzheimer's disease. A modeled cost-effectiveness analysis found that treatment with donepezil to be less costly and more effective than no treatment or treatment with memantine in Germany. However, the model drew on non-German population data and could have been more transparent with regard to 'back-end' processes. In addition, the authors would question the extent to which the differences in effectiveness between treatments would be considered clinically significant. Identifying sources of cost savings for donepezil remains an important issue for future consideration.

Special considerations for endoscopists on PEG indications in older patients

Undernutrition in frail elderly people is a pathological condition that needs to be recognized and addressed early. Neurological dysphagia is among the most frequent causes of this condition in the elderly but should be considered a terminal event in Alzheimer-type dementias. Tube feeding is an important resource for facilitating metabolic recovery in cachectic patients and is particularly successful in "bridging" and stabilizing therapies prior to major treatment able to cure the patient. Clinical management of tube feeding in "incurable" conditions is complex and becomes part of the palliative care and comfort provided in the terminal stages of illness. Non-specialized physicians are often unfamiliar with the theory and practice of end-of-life interventions, and the resulting decisions are in many cases actually contrary to patient comfort. These problems deserve to be more carefully addressed when the patient is unable to cooperate or express his/her preferences and needs. The success of percutaneous endoscopic gastrostomy has led to increasingly frequent referrals for placement in critically ill elderly patients. Endoscopists therefore become a key figure in stimulating rational, correct treatment of these patients.

The general public's willingness to pay for tax increases to support unrestricted access to an Alzheimer's disease medication

BACKGROUND

Alzheimer's disease (AD) is a neurodegenerative disorder highlighted by progressive declines in cognitive and functional abilities.

OBJECTIVE

Our objective was to assess the general public's maximum willingness to pay ((M)WTP) for an increase in annual personal income taxes to fund unrestricted access to AD medications.

METHODS

We randomly recruited 500 Canadians nationally and used computer-assisted telephone interviewing to administer a questionnaire. The questionnaire contained four 'efficacy' scenarios describing an AD medication as capable of symptomatically treating cognitive decline or modifying disease progression. The scenarios also described the medication as having no adverse effects or a 30% chance of adverse effects. We randomized participants to order of scenarios and willingness-to-pay bid values; (M)WTP for each scenario was the highest accepted bid for that scenario. We conducted linear regression and bootstrap sensitivity analyses to investigate potential determinants of (M)WTP.

RESULTS

Mean (M)WTP was highest for the 'disease modification/no adverse effects' scenario ($Can130.26) and lowest for the 'symptomatic treatment/30% chance of adverse effects' scenario ($Can99.16). Bootstrap analyses indicated none of our potential determinants (e.g. age, sex) were associated with participants' (M)WTP.

CONCLUSIONS

The general public is willing to pay higher income taxes to fund unrestricted access to AD (especially disease-modifying) medications. Consequently, the public should favour placing new AD medications on public drug plans. As far as we are aware, no other study has elicited the general public's willingness to pay for AD medications.

Composite Partial Likelihood Estimation Under Length-Biased Sampling, With Application to a Prevalent Cohort Study of Dementia

The Canadian Study of Health and Aging (CSHA) employed a prevalent cohort design to study survival after onset of dementia, where patients with dementia were sampled and the onset time of dementia was determined retrospectively. The prevalent cohort sampling scheme favors individuals who survive longer. Thus, the observed survival times are subject to length bias. In recent years, there has been a rising interest in developing estimation procedures for prevalent cohort survival data that not only account for length bias but also actually exploit the incidence distribution of the disease to improve efficiency. This article considers semiparametric estimation of the Cox model for the time from dementia onset to death under a stationarity assumption with respect to the disease incidence. Under the stationarity condition, the semiparametric maximum likelihood estimation is expected to be fully efficient yet difficult to perform for statistical practitioners, as the likelihood depends on the baseline hazard function in a complicated way. Moreover, the asymptotic properties of the semiparametric maximum likelihood estimator are not well-studied. Motivated by the composite likelihood method (Besag 1974), we develop a composite partial likelihood method that retains the simplicity of the popular partial likelihood estimator and can be easily performed using standard statistical software. When applied to the CSHA data, the proposed method estimates a significant difference in survival between the vascular dementia group and the possible Alzheimer's disease group, while the partial likelihood method for left-truncated and right-censored data yields a greater standard error and a 95% confidence interval covering 0, thus highlighting the practical value of employing a more efficient methodology. To check the assumption of stable disease for the CSHA data, we also present new graphical and numerical tests in the article. The R code used to obtain the maximum composite partial likelihood estimator for the CSHA data is available in the online Supplementary Material, posted on the journal web site.