"The duration of survival following a diagnosis of Alzheimer's disease depends critically on the subject's age at diagnosis. The results of this study indicate that the median survival of patients with Alzheimer's disease could range from nearly 9 years for persons diagnosed at age 65 to approximately 3 years for persons diagnosed at age 90 years," said Ronald Brookmeyer, PhD, professor of biostatistics at the Johns Hopkins Bloomberg School of Public Health.
Data for the study was collected from the Baltimore Longitudinal Study of Aging, which began in 1958 to monitor the effects of aging. The participants were asked to return for follow-up visits every two years to be examined and to answer questionnaires. From this study, Dr. Brookmeyer and his colleagues selected 921 participants who were age 55 or older in 1985 and had received some follow-up visits. Alzheimer's disease was diagnosed using several neuropsychological tests and deaths were recorded through September 1999.
The statistical analysis found that the median survival times ranged from 8.3 years for people diagnosed at age 65 to 3.4 years for people diagnosed at age 90. Persons diagnosed with Alzheimer's disease at age 65 could anticipate a 67 percent reduction in life span compared to those without Alzheimer's disease, while persons diagnosed at age 90 could anticipate a 39 percent reduction in life span. The researchers say Alzheimer's disease is associated with a greater proportionate reduction of life span
Contact: Tim Parsons
Johns Hopkins University Bloomberg School of Public Health