New research not only bolsters the concept that cognitive decline occurs over decades, but also shows that its effects can be detected as early as age 45 years.
The study, published today on bmj.com, analyzed data from 5198 men and 2192 women aged 45 to 70 years during a 10-year period beginning in 1997. Participants were part of the Whitehall II study, which examined social and occupational effects on disease and death rates among British government employees.
Researchers evaluated cognitive function by testing study participants’ memory, reasoning, vocabulary, and verbal fluency. Tests were given 3 times over 10 years.
Results showed measurable cognitive decline in all age groups on all test scores except vocabulary. The youngest men in the study, who were 45 to 49 years old at the start, had a 3.6% decline in their reasoning ability over 10 years, compared with a 9.6% decline in the oldest men, aged 65 to 70 years. Women aged 45 to 49 years also had a 3.6% decline in reasoning during the study, compared with a 7.4% decrease in women aged 65 to 70 years.
The authors said recent studies suggest that the progression of cognitive decline to dementia is a long-term process taking 20 to 30 years. They also noted that emerging evidence shows healthy lifestyle habits that reduce risks for cardiovascular disease also may reduce the risk of dementia. These findings, along with their own, support “aggressive control of behavioural and cardiovascular risk factors as early as possible,” the authors wrote.
Francine Grodstein, ScD, associate professor of medicine at Harvard Medical School in Boston, said in an accompanying editorial that the study sets “a new benchmark for future research and, eventually, clinical practice.”
Grodstein said dementia prevention efforts may need to start in adults as young as 45 years. She noted that most current dementia research focuses on people aged 65 years and older. “The major challenge will be to design prospective research studies that include much younger age groups—a dramatic change from the status quo.”
“Life expectancy continues to increase, and understanding cognitive ageing will be one of the challenges of this century,” the authors wrote.