New Study Examines Life Expectancy for Individuals Living with Dementia

Results published in the American Journal of Public Health indicate that the rate of dementia onset continues to increase into oldest ages and that years spent with dementia are few and represent a small percentage of life.

By Malissa Carroll
August 5, 2014

According to a first-of-its-kind study conducted by Sarah Tom, PhD, assistant professor in the Department of Pharmaceutical Health Services Research (PHSR) at the University of Maryland School of Pharmacy, and her colleagues at the Group Health Research Institute in Seattle, Wash., University of Washington Schools of Medicine and Nursing, Swedish Neuroscience Institute in Seattle, Wash., Harborview Medical Center in Seattle, Wash., and Harvard School of Public Health in Cambridge, Mass., the rate of dementia onset continues to increase into oldest ages and years spent living with dementia are few and represent a small percentage of an individual’s life.

“Previous studies have produced somewhat conflicting estimates of trends in dementia among older adults, and few have considered the risk of dementia onset and subsequent survival of individuals who have not yet been diagnosed with the condition,” says Tom, the study’s first author. “However, the number of individuals living with dementia worldwide is expected to increase as the population continues to age, and understanding dementia risk and survival with dementia in older adults will be essential for health policymakers.”

Published in the American Journal of Public Health, the study aimed to estimate dementia incidence rates as well as the average number of years that an individual is expected to live with and without the condition. Its results suggest that an individual’s risk for dementia increases by 60 percent between ages 85-89, and by 40 percent after age 90. Based on the study’s findings, a 70-year old could be expected to live 15 years without and two years with dementia.

Dementia is a general term used to describe symptoms associated with a decline in an individual’s cognitive abilities that are severe enough to interfere with his or her daily life. These symptoms can include problems related to memory, communication and language, ability to focus, reasoning and judgment, and visual perception. Dementia can be caused by a number of conditions, including Dementia with Lewy Bodies, vascular dementia resulting from a stroke, and Parkinson’s disease, but it most often affects individuals with Alzheimer’s disease.

According to the National Institute on Aging, Alzheimer’s disease is an irreversible, progressive brain disease that slowly destroys an individual’s memory and thinking skills, and eventually even the ability to carry out the simplest tasks.

Tom and her colleagues examined data from 3,605 individuals enrolled in the Group Health Research Institute’s Adult Changes in Thought study between 1994 and 2008 who were aged 65 years or older and did not have dementia at the time of enrollment. They used a three-state, piecewise homogenous Markov model to estimate life expectancy with and without dementia.

“We had a unique dataset that allowed us to follow the same group of people for nearly two decades to better understand patterns of dementia onset and survival,” says Tom. “Our study allowed us to incorporate the risk of dementia onset to estimate the years of life that an individual could be expected to live with dementia. It is one of the few studies that estimates the effect of dementia on the total population, which includes individuals with dementia, those who will develop dementia, and those who will not develop dementia.”

The researchers found that the rate of dementia onset increased among individuals aged 85 years and older. In addition, they noted that the average number of years a person is expected to live without dementia decreased with age for men and women – an estimate that accounted for the risk of developing dementia. However, women were expected to live more years with dementia than men when accounting for the risk of developing dementia.

The study was also the first to examine the relationship between an individual’s level of education and life expectancy with or without dementia, finding that life expectancy with dementia was longer among those who had at least a college degree, compared to those with lower levels of education.

“The consequences of dementia, particularly to the individuals affected and their families, are tremendous and a great fear in our aging society,” concludes Tom. “We hope our results will contribute to public health policies that help to delay dementia onset and improve the quality of life for patients with dementia and their caregivers.”

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