Dementia incidence may increase more slowly after age 90: Results from the Bronx Aging Study

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Abstract

Background: Dementia incidence increases dramatically from age 65 to age 85, with many studies reporting a doubling every 5 years. The incidence beyond age 85 is not established. Objective: To estimate the incidence of dementia as a function of age, with a particular focus on persons aged 85 and over. Methods: The Bronx Aging Study began in 1980 with 488 healthy, nondemented community-dwelling individuals, age 75 to 85. Persons in the study received clinical examinations and cognitive testing approximately every 12 months until death or loss to follow-up. The diagnosis of dementia was made using Diagnostic and Statistical Manual of Mental Disorders-III-R at diagnostic case conferences. Dementia incidence rates were calculated for 5-year age bands using person-time of follow-up as the denominator. Results: The relative incidence rate ratios of dementia for age 80 to 84 vs 75 to 79 was 2.32 (95% CI 1.23 to 4.37), the relative rate for age 85 to 89 vs 80 to 84 was 1.89 (95% CI 1.26 to 2.83), the relative rate for age 90 to 94 vs 85 to 89 was 1.49 (95% CI 0.86 to 2.58), while the relative rate for age 95 to 99 vs 90 to 94 was 1.31 (95% CI 0.38 to 4.46). Similar results were seen for men and women considered separately. Had the rate of increase from age 75 to 89 continued into the 90s, the study would have had 73% power to detect a significant difference between the rates for age 90 to 94 and 85 to 89 given the amount of observed follow-up time. Conclusions: Whereas dementia incidence continues to increase beyond age 85, the rate of increase appears to slow relative to that of 65- to 85-year-olds. These results suggest that dementia in the oldest old might be related not to the aging process itself but with age-associated risk factors.

Original languageEnglish (US)
Pages (from-to)882-886
Number of pages5
JournalNeurology
Volume65
Issue number6
DOIs
StatePublished - Sep 27 2005

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Dementia
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Independent Living
Diagnostic and Statistical Manual of Mental Disorders

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  • Neuroscience(all)

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Dementia incidence may increase more slowly after age 90 : Results from the Bronx Aging Study. / Hall, Charles B.; Verghese, Joe; Sliwinski, M.; Chen, Z.; Katz, Mindy Joy; Derby, Carol A.; Lipton, Richard B.

In: Neurology, Vol. 65, No. 6, 27.09.2005, p. 882-886.

Research output: Contribution to journalArticle

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abstract = "Background: Dementia incidence increases dramatically from age 65 to age 85, with many studies reporting a doubling every 5 years. The incidence beyond age 85 is not established. Objective: To estimate the incidence of dementia as a function of age, with a particular focus on persons aged 85 and over. Methods: The Bronx Aging Study began in 1980 with 488 healthy, nondemented community-dwelling individuals, age 75 to 85. Persons in the study received clinical examinations and cognitive testing approximately every 12 months until death or loss to follow-up. The diagnosis of dementia was made using Diagnostic and Statistical Manual of Mental Disorders-III-R at diagnostic case conferences. Dementia incidence rates were calculated for 5-year age bands using person-time of follow-up as the denominator. Results: The relative incidence rate ratios of dementia for age 80 to 84 vs 75 to 79 was 2.32 (95{\%} CI 1.23 to 4.37), the relative rate for age 85 to 89 vs 80 to 84 was 1.89 (95{\%} CI 1.26 to 2.83), the relative rate for age 90 to 94 vs 85 to 89 was 1.49 (95{\%} CI 0.86 to 2.58), while the relative rate for age 95 to 99 vs 90 to 94 was 1.31 (95{\%} CI 0.38 to 4.46). Similar results were seen for men and women considered separately. Had the rate of increase from age 75 to 89 continued into the 90s, the study would have had 73{\%} power to detect a significant difference between the rates for age 90 to 94 and 85 to 89 given the amount of observed follow-up time. Conclusions: Whereas dementia incidence continues to increase beyond age 85, the rate of increase appears to slow relative to that of 65- to 85-year-olds. These results suggest that dementia in the oldest old might be related not to the aging process itself but with age-associated risk factors.",
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AU - Hall, Charles B.

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AU - Sliwinski, M.

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AU - Katz, Mindy Joy

AU - Derby, Carol A.

AU - Lipton, Richard B.

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N2 - Background: Dementia incidence increases dramatically from age 65 to age 85, with many studies reporting a doubling every 5 years. The incidence beyond age 85 is not established. Objective: To estimate the incidence of dementia as a function of age, with a particular focus on persons aged 85 and over. Methods: The Bronx Aging Study began in 1980 with 488 healthy, nondemented community-dwelling individuals, age 75 to 85. Persons in the study received clinical examinations and cognitive testing approximately every 12 months until death or loss to follow-up. The diagnosis of dementia was made using Diagnostic and Statistical Manual of Mental Disorders-III-R at diagnostic case conferences. Dementia incidence rates were calculated for 5-year age bands using person-time of follow-up as the denominator. Results: The relative incidence rate ratios of dementia for age 80 to 84 vs 75 to 79 was 2.32 (95% CI 1.23 to 4.37), the relative rate for age 85 to 89 vs 80 to 84 was 1.89 (95% CI 1.26 to 2.83), the relative rate for age 90 to 94 vs 85 to 89 was 1.49 (95% CI 0.86 to 2.58), while the relative rate for age 95 to 99 vs 90 to 94 was 1.31 (95% CI 0.38 to 4.46). Similar results were seen for men and women considered separately. Had the rate of increase from age 75 to 89 continued into the 90s, the study would have had 73% power to detect a significant difference between the rates for age 90 to 94 and 85 to 89 given the amount of observed follow-up time. Conclusions: Whereas dementia incidence continues to increase beyond age 85, the rate of increase appears to slow relative to that of 65- to 85-year-olds. These results suggest that dementia in the oldest old might be related not to the aging process itself but with age-associated risk factors.

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