The Epidemic of Cognitive Decline

With the oldest old (men and women ages 85 years and over) as the fastest growing segment of the US population, and dementia incidence doubling every 5 years from ages 65 to 90 years, the stage is set for an epidemic of cognitive decline.  Maria Corrada and colleagues engaged subjects who were originally part of The Leisure World Cohort Study, and were 90 years of age or older as of January 1, 2003, to enroll in The 90+ Study.  The team assessed 330 resulting study subjects, primarily women (69.7%) between the ages of 90 to 102, and who showed no signs of dementia at baseline. The researchers identified 140 new cases of dementia during follow-up with 60% of those cases attributed to Alzheimer's disease (AD), 22% vascular dementia, 9% mixed AD and vascular dementia and 9% with other or unknown cause.  The researchers found the overall dementia incidence rate, based on 770 person-years of follow-up, was 18.2% per year. Rates increased with age from 12.7% per year in the 90-94 age group, to 21.2% per year in the 95-99 age group, to 40.7% per year in the 100+ age group. Incidence rates were very similar for men and women. Previous results from The 90+ Study found higher estimates of dementia prevalence in women (45%) compared to men (28%), a result also seen in other similar studies. Based on these findings, the team urges that: “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.”