Objective: The oldest old are the fastest growing segment of the US population, and accurate estimates of dementia incidence in this group are crucial for healthcare planning. Although dementia incidence doubles every 5 years from ages 65 to 90 years, it is unknown if this exponential increase continues past age 90 years. Here, we estimate age‐ and sex‐specific incidence rates of all‐cause dementia in people aged 90 years and older, including estimates for centenarians.Methods: Participants are from The 90+ Study, a population‐based longitudinal study of aging and dementia. Three hundred thirty nondemented participants aged 90 years and older at baseline were followed between January 2003 and December 2007. Age‐ and sex‐specific incidence rates of all‐cause dementia were estimated by person‐years analysis.Results: The overall incidence rate of all‐cause dementia was 18.2% (95% confidence interval [CI], 15.3–21.5) per year and was similar for men and women (risk ratio, 0.94; 95% CI, 0.65–1.37). Rates increased exponentially with age from 12.7% per year in the 90–94‐year age group, to 21.2% per year in the 95–99‐year age group, to 40.7% per year in the 100+‐year age group. The doubling time based on a Poisson regression was 5.5 years.Interpretation: Incidence of all‐cause dementia is very high in people aged 90 years and older and continues to increase exponentially with age in both men and women. Projections of the number of people with dementia should incorporate this continuing increase of dementia incidence after age 90 years. Our results foretell the growing public health burden of dementia in an increasingly aging population. ANN NEUROL 2010;67:114–121

Introduction: We forecast the prevalence of preclinical and clinical Alzheimer's disease (AD) and evaluated potential impacts of primary and secondary preventions in the United States.Methods: We used a multistate model incorporating biomarkers for preclinical AD with US population projections.Results: Approximately 6.08 million Americans had either clinical AD or mild cognitive impairment due to AD in 2017 and that will grow to 15.0 million by 2060. In 2017, 46.7 million Americans had preclinical AD (amyloidosis, neurodegeneration, or both), although many may not progress to clinical disease during their lifetimes. Primary and secondary preventions have differential impact on future disease burden.Discussion: Because large numbers of persons are living with preclinical AD, our results underscore the need for secondary preventions for persons with existing AD brain pathology who are likely to develop clinical disease during their lifetimes as well as primary preventions for persons without preclinical disease.

LIFE EXPECTANCY following a diagnosis of Alzheimer disease (AD) is important information for health planners, caregivers, patients, and their families. Such information is useful for planning the resources needed for the care of patients with the disease as well as for evaluating the effect on public health and for forecasting the future prevalence of the disease. However, there have been conflicting estimates of the duration of survival following a diagnosis of AD.^1-7 A study in 2001 indicated the overall survival of patients with dementia was only 3.3 years.¹ As pointed out by Wolfson et al,¹ some estimates are biased because they are based on the follow-up of individuals who were found to be prevalent with AD. This can lead to overestimation of survival because persons who die rapidly following a diagnosis of AD are excluded from the study. The resulting bias is called "length" or "survivor" bias, and as described by Wolfson et al,¹ a statistical adjustment is necessary to correct the bias.

Objective: The purpose of this study was to examine the role of multiple pathologies in the expression of dementia in the oldest-old. Methods: A total of 183 participants of The 90+ Study with longitudinal follow-up and autopsy were included in this clinical-pathologic investigation. Eight pathologic diagnoses (Alzheimer disease [AD], microinfarcts, hippocampal sclerosis, macroinfarcts, Lewy body disease, cerebral amyloid angiopathy, white matter disease, and others) were dichotomized. We estimated the odds of dementia in relation to each individual pathologic diagnosis and to the total number of diagnoses. We also examined dementia severity in relation to number of pathologic diagnoses. Results: The presence of multiple pathologic diagnoses was common and occurred more frequently in those with dementia compared with those without dementia (45% vs 14%). Higher numbers of pathologic diagnoses were also associated with greater dementia severity. Participants with intermediate/high AD pathology alone were 3 times more likely to have dementia (odds ratio = 3.5), but those with single non-AD pathologies were 12 times more likely to have dementia (odds ratio = 12.4). When a second pathology was present, the likelihood of dementia increased 4-fold in those with intermediate/high AD pathology but did not change in those with non-AD pathologies, suggesting that pathologies may interrelate in different ways. Conclusions: In the oldest-old, the presence of multiple pathologies is associated with increased likelihood and severity of dementia. The effect of the individual pathologies may be additive or perhaps synergistic and requires further research. Multiple pathologies will need to be targeted to reduce the burden of dementia in the population.

The authors explored the relation of body mass index (BMI; weight (kg)/height (m)²) and weight change to all-cause mortality in the elderly, using data from a large, population-based California cohort study, the Leisure World Cohort Study. They estimated relative risks of mortality associated with self-reported BMI at study entry, BMI at age 21 years, and weight change between age 21 and study entry. Participants were categorized as underweight (BMI <18.5), normal weight (BMI 18.5–24.9), overweight (BMI 25–29.9), or obese (BMI ≥30). Of 13,451 participants aged 73 years (on average) at study entry (1981–1985), 11,203 died during 23 years of follow-up (1981–2004). Relative to normal weight, being underweight (relative risk (RR) = 1.51, 95% confidence interval (CI): 1.38, 1.65) or obese (RR = 1.25, 95% CI: 1.13, 1.38) at study entry was associated with increased mortality. People who were either overweight or obese at age 21 also had increased mortality (RR = 1.17, 95% CI: 1.09, 1.25). Participants who lost weight between age 21 and study entry had increased mortality regardless of their BMI category at age 21. Obesity was significantly associated with increased mortality only among persons under age 75 years and among never or past smokers. This study highlights the influence on older-age mortality risk of being overweight or obese in young adulthood and underweight or obese in later life.

Research from JAMA Neurology — A Validation Study of the Dementia Questionnaire