Common sense does suggest that a large age gap would have implications for old age. Having someone to look after you in your dotage is wise, as is avoiding widowhood. A younger, healthier partner could make sense, at least from your side of the equation. Another study by Sven Drefahl of the University of Stockholm looked at people over the age of 50 in Denmark, and found that men with younger spouses survived for longer than those with ones of a similar age. The older their spouse, the worse their survival chances, even after controlling for things like education and wealth. Again, the link might not be causal: healthy men might be particularly able both to attract younger mates and live to a ripe old age. But mysteriously, this phenomenon does not appear to apply to women, where the bigger the age gap, the worse their survival chances, regardless of whether they were younger or older. In the case of women with younger husbands, Drefahl suggested, the gender difference could be due to women being less reliant on their partner for support, and so benefiting less from the energies of a younger spouse.

What evidence there is, therefore, vindicates the choices of OKCupid’s users: women should pick men who are as close as possible in age to them, while men should look for younger women.