People who prefer to be more active during the evening, and who go to bed later and get up later, have higher rates of metabolic dysfunction, cardiovascular disease, type 2 diabetes, psychiatric symptoms, mood disorders and winter depression.
But no scientist has ever examined whether these problems increase the risk of death. So two researchers, one from the US and another from the UK, joined forces to find out.
For the study, Kristen Knutson, associate professor of neurology at Northwestern University, Chicago, and Malcolm von Schantz, professor of chronobiology from the University of Surrey, analyzed data gathered from 433,268 men and women aged between 38 and 73.
The researchers asked these people a single question: Are you a definite morning type, definite evening type, a moderate morning type or a moderate evening type? Then the participants were followed up over 6½ years.
After adjusting the findings to take account of age, sex, ethnicity, smoking, body mass index, duration of sleep, socioeconomic status and health disorders, it turned out there was a sharp difference between definite evening types and definite morning types.
Increased risks for the former were found for psychological disorders (plus 94%), diabetes (plus 30%), neurological disorders (plus 25%), gastrointestinal disorders (plus 23%), respiratory disorders (plus 22%) - and a 10% increased risk of death.
The researchers didn't find any difference between men and women but the heightened risk of death was strongest among the oldest participants.
There was no increased risk of death among moderate types, and fortunately, the definite evening types only made up 9% of the whole group. However, that is still a sizable chunk of people.
Disrupts Body Physiology
Whether someone is a morning or evening person is determined in part by a genetic component, calculated to account for 21% to 52% of their preference. The rest of the predisposition is influenced by aging and environmental factors that are partly under our control.Commenting on the findings, Dr. Knutson said, “I think the problem arises because a night owl is trying to live in a morning lark world. If the body is expecting you to do something at a certain time like sleep or eat and you’re doing it at the quote ‘wrong’ time, then your body’s physiology may not be working as well.
“If we can recognize these chronotypes are, in part, genetically determined and not just a character flaw, jobs and work hours could have more flexibility for owls.”
Professor von Schantz added, “This is a public health issue that can no longer be ignored. We should discuss allowing evening types to start and finish work later, where practical. And we need more research about how we can help evening types cope with the higher effort of keeping their body clock in synchrony with sun time.”
While it is not easy for confirmed night owls to adjust, if this applies to you, try getting up and going to bed a few minutes earlier each day until it starts to make you feel uncomfortable. Then keep to this new schedule.
Also, get into the habit of completing chores earlier in the day and expose yourself to less artificial light in the evenings.
Dr. Knutson recommends night owls in particular eat a healthy diet and take regular exercise.
