Twelve years of Finnish register data link an evening chronotype in midlife to a 1.7-fold higher likelihood of a disability pension.
Some people spring out of bed at dawn. Others do their best thinking after midnight. That internal timing, known as chronotype, has a strong genetic basis and stays fairly stable through adulthood. A new study suggests it may also shape how long people are able to keep working.
In research published in Occupational & Environmental Medicine, investigators drawing on the Northern Finland Birth Cohort 1966 found that people who identified as evening types at age 46 were about 1.7 times as likely as morning types to receive a disability pension over the following 12 years. The association held for both men and women, and it persisted after the researchers accounted for education and type of occupation.
A cohort followed from birth
The Northern Finland Birth Cohort began in 1966 and includes about 96 percent of people born that year in Finland’s two northernmost provinces, making it one of the most complete population records of its kind. In 2012, when participants were 46, they answered questions about how easily they woke up, how tired they felt in the first half hour after waking, when they preferred to work, and whether they considered themselves morning or evening people.
The baseline sample comprised 5,679 people: 2,597 men and 3,082 women. Evening types were a minority, at 9.7 percent of men and 12.4 percent of women. Morning types made up about 46 percent of men and 44 percent of women, with the rest falling in between.
The researchers then tracked participants through Finland’s national work and pension registers. Over the 12-year follow-up, 135 men (5.2 percent) and 249 women (8.1 percent) were granted a first disability pension. In Finland, such pensions are awarded only after severe and long-lasting declines in health, so they serve as a hard marker of lost working capacity rather than a minor setback.
Why the evening type may wear down
The authors believe poorer health among evening types is the main driver. Earlier research has tied an evening chronotype to less healthy habits and to chronic misalignment between a person’s internal clock and the schedules society imposes, a mismatch that can disrupt sleep. Over decades, those pressures may add up. The researchers suggest that some evening types may already have experienced a decline in health by their 50s and early 60s that eroded their ability to work.
The stakes extend beyond individual workers. Evening types “represent a significant proportion of the population,” the authors write, “and their health and ability to continue working until retirement age pose challenges for sustainable economies.”
What the study can and cannot say
The study’s strengths include a large sample spanning every economic sector and occupation, a long follow-up period and outcomes drawn from official registers rather than self-report. The team also used genetic information to support the idea that chronotype is a stable trait.
But the design is observational, so it cannot show that being a night owl causes people to leave work early. And because chronotype and health were measured once, at age 46, the analysis could not fully account for changes in participants’ health or circumstances over the following years.
The findings nonetheless add to a growing body of work suggesting that rigid, early-starting schedules may not suit everyone equally. For employers and policymakers facing ageing workforces, the question of how to accommodate different body clocks may prove to be more than a matter of personal preference.
Notes
- Evening chronotype and disability pensions: 12-year register-based follow-up of middle-aged adults from the Northern Finland Birth Cohort 1966. Occupational & Environmental Medicine, 29 September 2026. DOI: 10.1136/oemed-2026-110995.
- BMJ Group. “Night owls may struggle to continue working until official retirement age.” EurekAlert!, 29 September 2026. https://www.eurekalert.org/news-releases/1145517.
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