"This research is a first attempt to shed light on important, but understudied, adverse consequences of gender inequality on women's health in later life," said Eric Bonsang of Columbia University in New York, who is lead author of the study published in the journal Psychological Science.
"It shows that women living in gender-equal countries have better cognitive test scores later in life than women living in gender-unequal societies. Moreover, in countries that became more gender-equal over time, women's cognitive performance improved relative to men's," added Bonsang, who is also affiliated with University Paris-Dauphine in France.
The researchers had noticed that the differences in men's and women's scores on cognitive tests varied widely across countries.
In countries in northern Europe, for example, women tend to outperform men on memory tests, while the opposite seems to be true in several southern European countries.
"This observation triggered our curiosity to try to understand what could cause such variations across countries," Bonsang said.
While economic and socioeconomic factors likely play an important role, the researchers wondered whether sociocultural factors such as attitudes about gender roles might also contribute to the variation in gender differences in cognitive performance around the globe.
They hypothesised that women who live in a society with more traditional attitudes about gender roles would likely have less access to opportunities for education and employment and would, therefore, show lower cognitive performance later in life compared with men of the same age.
The researchers analysed cognitive performance data for participants between the ages of 50 and 93, drawn from multiple nationally representative surveys. Together, the surveys provided data for a total of 27 countries.
Overall, the data showed considerable variability in gender differences in cognitive performance across countries.
In some countries, women outperformed men -- the female advantage in cognitive performance was highest in Sweden.
In other countries, however, men outperformed women -- the male advantage was highest in Ghana.
The researchers found that women in countries with less traditional attitudes were likely to have better cognitive performance later in life relative to women in more traditional countries.
"These findings reinforce the need for policies aiming at reducing gender inequalities as we show that consequences go beyond the labour market and income inequalities," Bonsang said.