A very large study of self-employed people living in France finds those who retired later had a lower risk of being diagnosed with dementia, in line with the idea that you either "use it or lose it."
Carole Dufouil of the Bordeaux School of Public Health, and colleagues, found that the risk of being diagnosed with dementia went down for each year of working longer.
The study appears to confirm earlier research that suggests lifelong mental stimulation and challenge may protect against Alzheimer's and other forms of dementia.
Dufouil, who is director of research in neuroepidemiology at the school's National Institute for Health and Medical Research (INSERM - Institut national de la santé et de la recherche médicale), says in a statement:
"Our data show strong evidence of a significant decrease in the risk of developing dementia associated with older age at retirement, in line with the 'use it or lose it' hypothesis."
"The patterns were even stronger when we focused on more recent birth cohorts," she adds.
The results of the study, which covered more than 429,000 self-employed workers living in France, were presented at AAIC 13, the Alzheimer's Association International Conference in Boston, MA, on Monday.
For the study, the researchers used health and insurance databases of self-employed people who were living and had been retired for an average of 12 years by the end of 2010.
The rate of diagnosed dementia in this group was 2.65%, said the researchers.
Waiting another 5 years for retirement means lower Alzheimer's risk
The researchers found that workers who retired at 65 years of age had a 14% lower rate of Alzheimer's diagnoses than those who retired at age 60.
The results also showed that for each year retirement was delayed, there was an increased delay in the presence of Alzheimer's.
Dementia, which affects mainly people over 60, is a disease where mental ability declines, usually slowly, leading to impairment of memory, thinking and judgement, and deterioration of personality.
Dufouil says the study findings are in line with the idea that professional activity, by providing mental stimulation and social engagement, is potentially protective against dementia.
"As countries around the world respond to the aging of their populations, our results highlight the importance of maintaining high levels of cognitive and social stimulation throughout work and retired life, and they emphasize the need for policies to help older individuals achieve cognitive and social engagement," she urges.
The International Longevity Center-France, which is headed by Professor Françoise Forette, was also involved in coordinating the study.
Mental stimulation and social engagement are not the only activities linked to lower dementia risk. A study published earlier this year found that being physically active in middle age is also tied to lower dementia risk later in life.
And a Spanish trial found that brain power in older people at risk for vascular dementia seems to improve more from a Mediterranean diet with added mixed nuts or extra virgin olive oil than from a low-fat diet that is typically recommended for preventing heart attack and stroke.