Napoleon Bonaparte famously claimed to need only four hours of sleep a night as he transformed the chaos of France's revolution into a military machine that overwhelmed most of Europe.
But six years after his defeat at Waterloo in 1815, the fallen emperor died at just 51, with stomach cancer given as the cause. An 1818 doctor’s note listed multiple health concerns reported by Napoleon during his exile.
These days, sleeping too little is widely acknowledged as unhealthy, with multiple studies suggesting it leaves a body more vulnerable to disease and premature ageing and a mind more inclined to see cognitive decline earlier in life.
But at the same time, getting too much sleep does not have the opposite effect, according to doctors at Columbia University Irving Medical Center, whose latest research points to getting between 6.4 and 7.8 hours as the optimum duration.
"Too little and too much sleep are associated with faster ageing in nearly every organ, supporting the idea that sleep is important in maintaining organ health within a coordinated brain-body network, including metabolic balance, and a healthy immune system," said Junhao Wen, assistant professor of radiology at Columbia.
In a study published in Nature, the team assessed data for half a million people in the UK stored in the UK Biobank, finding that "both short sleep and long sleep were associated with faster ageing" as well as a possible connection to the likelihood of an irregular sleeper developing depression.
"The least amount of ageing occurred in people who reported between 6.4 and 7.8 hours of sleep per day," they reported, a finding that suggests "both insufficient and excessive sleep may be markers of poorer overall health across the body."
Anything less than six hours is considered short sleep, according to the team, while getting more than eight hours is probably too much.