Libido loss doesn’t usually happen suddenly – it’s not like catching a cold where you wake up one morning and whoops, there it is. It can be a gradual process. Though difficult to define precisely, Laumann measures it as follows: “It is a lack of interest in sex for several months of the past year.”
Frequency of sexual activity is not the best measure of sexual interest – so many circumstances can get in the way of an encounter, even if the desire is there. But if you are in a committed relationship and having sex less often than the norm — about once a week – you might ask yourself whether you are happy with things as they are.