Do retired people tend to perform more poorly on cognitive tests than working people because you’re more likely to retire if your mental skills are starting to decline, or because retirement dulls the brain?

For nearly 20 years the United States has surveyed more than 22,000 Americans over age 50 every two years, and administered memory tests. A similar survey has also been taking place in Europe. A comparison of the 2004 data for the U.S., England, and eleven European countries (Austria, Belgium, Denmark, France, Germany, Greece, Italy, The Netherlands, Spain, Sweden, and Switzerland) has now revealed differences in the level of cognitive performance among older adults between the countries (the 60-64 year age group was used as it represents the greatest retirement-age difference between nations).

These differences show some correlation with differences in the age of retirement. Moreover, the differences also correlate to differences in government policy in terms of pensions — supporting the view that it is retirement that is causing the mental decline, not the decline that brings about early retirement.

Memory was tested through a simple word recall task — recalling a list of 10 nouns immediately and 10 minutes later. People in the United States did best, with an average score of 11 out of a possible 20. Those in England were very close behind, and Denmark and Sweden were both around 10. Switzerland, Germany and the Netherlands, and Austria were all clustered between 9 and 9 ½; Belgium and Greece a little lower. France averaged 8; Italy 7; Spain (the lowest) just over 6.

Now when the average cognitive score is mapped against the percentage of retired for 60-64 year olds, the points for each country (with one exception) cluster around a line with a slope of -5, indicating that there is a systematic relationship between these two variables, and that on average being retired is associated with a lower memory score of about 5 points on a 20-point scale. This is a very large effect.

But the correlation is not (unsurprisingly) exact. Although the top scorers, U.S., England and Denmark, are among those nations who have lower retirement rates at this age, Switzerland has the same levels as the U.S., and Sweden has the fewest retired of all (around 40% compared to around 47% for the U.S. and Switzerland). Most interesting of all, why does Spain, which has around 74% retired, show such a low cognitive score, when five other countries have even higher rates of retirement (Austria has over 90% retired)?

There are of course many other differences between the countries. One obvious one to look at would be the degree to which older people who are not working for pay are involved in voluntary work. There’s also the question of the extent to which different countries might have different occupation profiles, assuming that some occupations are more mentally stimulating than others, and the degree to which retired people are engaged in other activities, such as hobbies and clubs.

The paper also raises an important point, namely, that retirement may be preceded by years of ‘winding-down’, during which workers become progressively more reluctant to keep up with changes in their field, and employers become increasingly reluctant to invest in their training.