About the time when my children learnt to sleep through the night, I lost the knack. Waking up tired is one of the quiet horrors of middle age. I’ve recently become addicted to my Fitbit watch, which tracks sleep, and my new first-thing ritual is to scan the dismal numbers from the night before: the hour-plus awake, the preponderance of light sleep and the struggle to reach seven hours.

Fitbit (I’ve come to think of him as a friend) offers benchmarks to reassure me that all this is pretty typical for my peer group. By middle age, we have fewer deep-sleep brain waves, more body pain and weaker bladders, explains Matthew Walker, a sleep expert at the University of California, Berkeley. Victor Horta, the great Brussels architect of art nouveau, seems to have been so plagued by night-time toilet trips that he built a urinal into his bedside wardrobe.

Old people sleep even worse but they generally have more time to spend trying, which might explain why 45- to 54-year-olds emerged as “the most sleep-deprived age group” in a survey of 5,007 Britons for the UK’s Sleep Council in 2013.