Alzheimer s study: Authors perhaps forgot about cause and effect

Related articles


Adding to the growing body of research that cognitive and social stimulation in seniors is beneficial, a new study purports to have found that retiring later in life makes one less likely to develop Alzheimer s disease (AD).

Researchers collected data from an insurance provider for 430,000 self-employed shopkeepers and craft workers in France. Of those, about 11,000 developed Alzheimer s or other dementias following retirement. The study reports that those individuals who retired at 65 were 14.6 percent less likely to develop Alzheimer s than those individuals who retired at 60, going so far as to attribute a 3.2 percent reduced AD risk per extra year of working.

Study authors point out several limitations of the study, mainly that results may not be generalizable to other professions due to how specific the sample size was. Additionally, the study failed to take into account factors such as education which have the potential to affect dementia onset. Lastly, Dr. David Knopman of the Mayo Clinic, in an editorial comment, adds that other factors 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. They make the risk of Alzheimer s disease a little more complex and these things can t be ignored.

ACSH s Dr. Gilbert Ross points to another consideration. This study fails to consider one of the most important epidemiological fallacies, Post hoc ergo propter hoc: the false conclusion that if something occurs after a prior event, the first event must have caused the later one. Is it really working longer which is protective against AD? Or, are people who show signs of cognitive impairment, an early sign of AD, more likely to retire early? From the results of the study, it cannot be concluded that working or maintaining high levels of cognitive stimulation, are responsible for fending off Alzheimer s.