IT’S the curse of the 21st century: too many people working crazy shifts and double jobs, trying to keep the wolf and the bankers from the door.
The result - obesity, diabetes, heart attacks, strokes. People who regularly put in overtime and work 10- or 11-hour days increase their heart disease risk by nearly two-thirds.
A study by Finnish researcher Mianna Virtanen of 6,000 British civil servants published in the European Heart Journal found that after accounting for risk factors such as smoking, those who worked three to four hours of overtime a day ran a 60pc higher risk of heart attacks.
Francesco Cappuccio, Professor of Cardiovascular Medicine and Epidemiology at the University of Warwick, is running a huge series of studies called Sleep, Health and Society. Prof Cappuccio is using metanalysis - pulling together lots of studies of population from the last 60 years - to study how long people sleep and how that is related to the illnesses that stalk and kill them.
“The results show a dual effect,” says Francesco. “Those who were consistently sleeping five hours or less per night tended to have about a 12pc increased risk of dying early.”
And people who sleep too long have a 30pc bigger chance than normal of dying early. But it is thought that the risk from longer sleep is mainly because people spend more time asleep when they’re falling ill with a serious disease. Very long sleep can also be a sign of depression.
“We’ve pulled together studies carried out in Europe, in America and in East Asia,” says Francesco - and the results were the same everywhere.
Shift work has led us to sleep less and less over the last 50 years, he says, and shift workers have a worse health outcome compared to people who work an old-fashioned working day.
This bad health is consistent over all classes - labourers, pilots, journalists, doctors - who work odd shifts that affect their sleep. Laboratory studies of short sleep show that it sends your hormones haywire and makes mad neuro-endrocrine changes. In extreme short sleep your cortisol increases, your glucose intolerance gets worse, your insulin resistance increases. “These are the precursors of diabetes.”
Your blood pressure and cholesterol go up, and your adrenaline and noradrenaline secretions, the stress hormones. “Many other changes of this kind, like ghrelin and leptin, the hormones regulating appetite, which work in a see-saw fashion. They will increase your appetite and reduce your metabolic expenditures.
“When you sleep less, these hormones move in a way that will stimulate your hunger and appetite, and reduce your metabolic expenditures.”
The link between obesity and sleep isn’t that clear, though - it’s complicated by the fact that weighty people find it harder to breathe when they’re lying down, which may make sleep difficult.
The real terror is cardiovascular disease - strokes and heart attacks - which kill one in three men, and one in four women. “A 12pc risk of death in short sleepers… would equate to over 6.3 million attributable deaths in the UK in people over 16,” says Francesco, “and 25 million in the US.” For coronary heart disease the risk is estimated at 23pc of the population.
So if you’re thinking of taking that high-powered job, with its crazy working hours, think again. The hours just might not be worth it.
© Lucille Redmond
First published in the Evening Herald, Dublin, Ireland