Morning Larks More Productive at Work and Have Fewer Disability Pensions Interview with:
Dr Tapio Räihä
Center for Life Course Health Research
University of Oulu, Oulu, Finland What is the background for this study?

sleep-work-occupational-chronotypeResponse: In ageing societies, understanding risk factors for pre-term disability pensions and poor work ability is an important research priority. We studied whether individual-level chronotype could contribute to these.  Previous research has shown that evening chronotypes (E-types) have poorer health compared with morning chronotypes (M-types), and that E-types may have difficulties to function during standard morning working hours. This study was the first population-level study with register linkage to find out whether eveningness would be associated with poor work ability and disability pensions, too.

We surveyed chronotype (with the Morningness–Eveningness Questionnaire) among 5831 non-retired Finns born in 1966 when they were at age 46 years, and compared it with their current perceived work ability. We then followed the emergence of new registered disability pensions during the next 4 years. Multivariate logistic and Cox regression analyses of the associations between chronotype and the outcomes were separately adjusted for sleep, health and behaviours, sociodemographic and economic factors, or working times What are the main findings?

Response: E-types represented 10% of men and 12% of women. E-types gave worse ratings on their sleep and health compared to earlier chronotypes. Although E-types were more often found among those whose working with schedules including night shifts, the vast majority of any chronotype worked in day jobs, even about 70% of E-types.

Compared with M-types, E-types had more than a doubled risk for perceiving poor work ability. In the unadjusted models, the odds ratios (and their 95% confidence intervals) for men and women were 2.24 (1.62 to 3.08) and 2.33 (1.74 to 3.10), respectively. The association between E-type and poor work ability was robust, as it withstood adjustments from several different perspectives, including working times, and fell subtly below statistical significance only in the fully adjusted model in men but not in women. In the fully adjusted model, overadjustment is possible.

During the next 4 years, 3.0% of E-type men and 1.0% of M-type men were granted disability pension, which represented a three-fold higher hazard ratio for E-type men compared to M-types (HR 3.12, 95% CI 1.27 to 7.63). This association remained statistically significant in other models but was diluted when multiple sleep variables or working times were taken into account. In E-type women, the hazard ratios for pensions were smaller and non-significant. However, since the numbers and proportions of these indeed early disability cases were expectedly small, care must be taken in interpreting the results. What should readers take away from your report?

Response: We suggest eveningness to be considered and further studied as a risk factor for poor work ability and early disability retirement in middle age. Furthermore, the modellings give support to the assumption that factors related to sleep and working times might be of relevance regarding this association. Although any new observational findings need to be confirmed in other studies, our results are well in line with previous evidence on eveningness and functioning, speaking for the plausibility of these findings.

In accordance, promoting better matching of the internal and social rhythm could be worthwhile to support work careers of E-types. Actions could be targeted to the individual, the environment or both. We encourage individual-level promotion of healthy lifestyle and good sleep among E-types as well as organizational-level planning of work schedules providing opportunities for flexibility according to individual chronotypes. In sum, we suggest that individual chronotype be considered in attempts to lengthen work careers. What recommendations do you have for future research as a result of this work?

Response: Additional longitudinal studies in diverse settings and in different age groups are needed to confirm our results, to study causal mechanisms and to develop interventions. Using objective chronotype and sleep measures, as well as addressing potentially co-occurring personality factors and work-related variables including worktime control could add value. 


Evening chronotype is associated with poor work ability and disability pensions at midlife: a Northern Finland Birth Cohort 1966 Study, Occupational & Environmental Medicine, DOI: 10.1136/oemed-2020-107193



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Last Updated on February 27, 2021 by Marie Benz MD FAAD