There are people who are more alert and productive during evening hours. Their circadian rhythm has naturally shifted, and they find it difficult to wake up early in the morning and feel more energetic at night.
A recent 12-year-long Finnish study has discovered that such ‘night owls’ possess a 70% higher risk of attaining a disability pension as they approach their retirement age. However, this higher risk was no longer statistically significant after researchers adjusted for factors including self-rated health, body mass index, smoking, alcohol consumption and physical activity.
Researchers from the University of Oulu and other Finnish institutions conducted this observational study with an objective of determining whether a person’s chronotype at age 46 is interlinked with receiving a disability pension over the following 12 years.
There have been previous studies that have determine that evening chronotypes tend to have poorer health and tend to have more difficulties in working life, but their association with accessing disability pensions had not been established yet.
Hence, the observational study establishes an association between the chronotype of a person and how likely they are to receive a disability pension in Finland.
Some people might assume that disability pension refers to government welfare money given to a person with permanent physical disability.
However, in Finland, disability pension is granted when a person's health has deteriorated significantly for a prolonged period of time, affecting their ability to work. In this study, disability pension was defined broadly to include full and partial disability pensions, as well as temporary and partial rehabilitation allowances.
The researchers specifically selected people born in 1966 in Northern Finland. The study consisted of 5,679 adults that were followed for around 12 years. Among these, 2,597 were men and 3,082 were women.
The selected participants were 46-years-old in 2012, when they were asked to answer certain questions regarding their daily life cycle, like how easily they woke in the morning, how tired they felt during the first half hour, and when they preferred to work.
These participants were observed for 12 years through Finnish national register data until 2023. The participants were categorized into different chronotypes on the basis of their natural preference of sleeping and being active at particular times of the day.
The participants were divided into three different chronotypes: morning, evening, and intermediate, on the basis of an assessment that consisted of questions related to their daily life. The researchers used a shortened Morningness-Eveningness questionnaire to determine whether participants naturally tended to be more active in the morning, evening, or somewhere in between.
The researchers analyzed the national pension records of these participants in 2023 and connected it to the particular participant’s chronotype.
Initially, the study highlighted that the people with evening chronotypes were 70% more prone to diminished health and accessing disability pensions.
However, the increased risk became statistically non-significant after researchers adjusted the factors and decided to include self-rated health, body mass index, smoking, alcohol consumption, and physical activity.
8.3% of evening type men received a disability pension in comparison to the 5% of morning types. And in women, the figures were 12.1% and 7.2%, respectively.
During the follow-up period, 135 men (5.2%) and 249 women (8.1%) received their first disability pension.
Overall, the study concluded that evening types had about 1.7 times the higher risk of attaining a disability pension compared with morning types.
The results thus suggest that being an evening type itself is not the main reason for higher disability-pension risk. Instead, other factors like poorer health and lifestyle also account for much of the association.
According to this study, no. Staying up late cannot be linked to disability directly. It is important to note that this research is an observational research. This means that it only identifies an association and does not establish the fact that late-night sleep preference causes disability. The researchers also highlighted the need for the findings to be studied in other populations and healthcare systems. The researchers also noted that participants’ health and life circumstances may have changed during the 12-year follow-up, and these changes could not be taken into account.
(Rh/MF/MSM)
