EDITOR—Hippisley-Cox et al observed significant similarities for disease between spouses in a large sample of 8386 couples recruited through general practice.1 They think that shared environmental factors may cause these similarities but reject assortative mating as an explanation.

In a sample from the Netherlands twin register we could not replicate their spouse similarities for asthma, depression, diabetes, and cardiovascular disease, possibly because of our smaller sample size of 2152 spouse pairs.2 When we examined health behaviour in a larger sample we found good associations between spouses for smoking, …