By drawing on the database from the ICTUS/DSA study (Impact of Cholinergic Treatment Use/Data Sharing Alzheimer), whose objective was to examine the natural history of Alzheimer’s disease and the effect of symptomatic treatments involving the use of inhibitors and the socioeconomic impact of the condition, researchers revisited a British study which tended to show a non-negligible link between the age of retirement and the onset of the disease. The results showed that there is an association, but to a lesser degree than previously suggested.

The only certainty that emerged from the study was that, in order to untangle the relationship between retirement age and changes in cognitive functioning, including the emergence of a neurodegenerative dementia, there are probably a vast number of variables that need to be taken into account. Article published in PLoS One.

Some twenty years ago, the concept of “cognitive reserve” emerged which held that all activities that we undertook in our lives help us to develop a kind of mental reserve which can enable us to compensate for the cognitive decline associated with normal aging or Alzheimer’s disease. Today, scientific literature abounds with articles that highlight the protective role of different proxy that are supposed to provide the cognitive reserve such as: having a high level of schooling, an active lifestyle, a profession that requires a certain complexity, having pastimes that are culturally enriching, having a well-developed social network...

Nevertheless, the mechanisms that underpin the cognitive reserve remain relatively unknown. There is a commonly-established link between this concept and that of brain plasticity. Put another way, the richer our activities are from a cognitive point of view, the more we develop alternative networks that we can use to counteract the deficiency of networks affected by natural or pathological ageing. But is there a direct correspondence between cognitive reserve and brain reserve? Some dispute this, arguing that the first covers a much vaster field than the second, in particular, because it calls into action psychological factors (motivation, for example) which make for better use of the available cognitive resources.

A disputed study

Whatever the case may be, many studies have established a link between factors contributing to the construction of cognitive reserve on one hand and a decrease in the risk of developing Alzheimer’s as well as an increase in the period of time preceding its eventual onset.

As pointed out by Catherine Grotz, a young doctoral student and research fellow at the Belgian Fund for Scientific Research (F.R.S.-FNRS), in the Psychology of Senescence Unit directed at the University of Liege by Professor Stéphane Adam, the professional sphere can be considered to be an environment that lends itself to developing social contacts and the exercise of cognitively stimulating activities, two sources which enrich the cognitive reserve. In an article entitled Retirement age and the age of onset of Alzheimer's disease: Results from the ICTUS study (1), published in February 2015 in the journal PLoS One and of which she is the first author, the researcher also points out that several studies have demonstrated that leaving the professional sphere brings about radical changes in an individual’s way of life and can affect their cognitive function. However, for the moment only two research articles relating to the impact of retirement on the risk of developing Alzheimer’s and the time of its onset have been published.

Published in 2010 in the International Journal of Geriatric Psychiatry, the first article (2) to deal with this subject was completed under the direction of Michelle K. Lupton, of King's College London. Catherine Grotz and an international team of researchers wanted to revisit the data from this article especially since the links between retirement and cognition constitute a particularly sensitive subject which may become a political football at a time when attempts are being made to extend the age of retirement under the pretext that this would be good for the health of all the individuals concerned.

(1) Grotz C, Letenneur L, Bonsang E, Amieva H, Meillon C, Quertemont E, Salmon E, Adam S, ICTUS/DSA group, Retirement age and the age of onset of Alzheimer's disease: Results from the ICTUS study, 2015 Feb 25;10(2):e0115056. doi: 10.1371/journal.pone.0115056.eCollection 2015.