Link Seen in Age at Retirement and Risk of Alzheimer's (CME/CE)
French retirees who had stopped working relatively late in life were less likely to develop Alzheimer's disease, a researcher reported here.
Analysis of a French healthcare insurer's records indicated that, for each year after age 60 at which a person retired, the risk of subsequently developing Alzheimer's disease was lower by 3.2% (HR 0.968, 95% CI 0.962-0.973), said Carole Dufouil, PhD, of INSERM in Bordeaux, France.
After adjusting for certain other risk factors, individuals retiring at 65 were 14.6% less likely to develop Alzheimer's disease than those retiring at 60, she said at a press briefing held prior to her formal presentation at the Alzheimer's Association International Conference.
The results were "in line with the use-it-or-lose-it hypothesis," she said, which holds that people who remain mentally active develop dementia at lower rates than those who don't.
Data for the study came from an insurance provider for self-employed workers in France, mainly shopkeepers and craft workers, Dufouil explained. Records for some 430,000 pensioners as of December 2010 were analyzed, including 11,397 who were considered to have developed Alzheimer's disease or related dementias after retirement.
The analysis excluded individuals whose records indicated a Parkinson's disease diagnosis at any time and also those with apparent dementia at retirement.
Onset of Alzheimer's disease was defined as a diagnostic code of ALD15 in the French healthcare system, which refers to "Alzheimer's disease and related disorders," or purchase of anti-dementia drugs such as memantine (Namenda) or acetylcholinesterase inhibitors.
Because they had such a large data set to work with, Dufouil and colleagues also conducted analyses to determine if the relationship between retirement age and Alzheimer's risk differed among subgroups.
There were statistically significant differences in two groups -- men versus women and craft workers versus shopkeepers -- but all still showed a significant decrease in risk of at least 2% for each year beyond age 60 for retirement.
Stratification by age of birth or age at Alzheimer's disease diagnosis also did not make a great difference in results, Dufouil said.
She added that sensitivity analyses in which some individuals were excluded -- such as those with diagnoses within 5 or 10 years of retirement, those retiring after age 75, and those with relatively short periods of self-employment before retirement -- also confirmed the topline results.
Dufouil noted several limitations to the study: The findings might not be applicable to other occupational types, the definition of new-onset dementia could be questioned, and the data lacked information on formal educational attainment and certain other important risk factors, she said.
Nevertheless, she said the results added to the growing body of evidence that "maintaining high levels of cognitive and social stimulation" is beneficial in seniors.
David Knopman, MD, of the Mayo Clinic in Rochester, Minn., who moderated the press briefing, cautioned that the findings may not entirely be an expression of "cognitive reserve," the idea that individuals who exercise their brains regularly throughout life can retain normal cognitive function despite physical injuries and insults.
He noted that other factors that co-associate with mental activity -- such as the ability to avoid other health risks, and the consequent lower risk of cardiovascular disease that can independently impair cognitive function -- also have to be considered.
"All of these things bear on the ability of the brain to withstand the onslaught of something like Alzheimer's disease," he said. "[They] make the risk of Alzheimer's disease a little more complex and these things can't be ignored."
