People who have a natural preference for staying up late tend to have poorer health habits, including sleep habits, which in turn is associated with reduced wages, according to new research published in Economics and Human Biology. The findings shed light on the links between people’s natural sleep patterns, known as chronotypes, and their financial well-being in midlife.
While previous research has shown varying associations between sleep duration and wages, there have been inconsistencies and a lack of understanding about the underlying mechanisms driving these relationships. The researchers aimed to provide a more comprehensive and nuanced understanding of how sleep, as indicated by chronotype, affects wages and the potential pathways involved.
Chronotype refers to an individual’s natural preference for the timing of their daily activities, particularly their sleep-wake cycle. It is closely related to an individual’s internal circadian rhythm, which is the internal biological clock that regulates various physiological and behavioral processes over a roughly 24-hour period. This circadian rhythm influences when we feel most alert, awake, and productive, as well as when we feel more inclined to sleep.
People exhibit different chronotypes based on their inherent circadian rhythms. These can be broadly classified into three categories:
Morning Types (Larks): Morning types are individuals who naturally prefer to wake up early in the morning and are most alert during the early hours of the day. They tend to feel tired and ready for sleep earlier in the evening.
Evening Types (Owls): Evening types are individuals who naturally prefer to stay awake and active during the late hours of the night. They tend to feel more alert and awake in the evening and may struggle with early morning activities.
Intermediate Types: Some individuals fall in between morning and evening types, with a chronotype that falls somewhere in the middle. They may feel more alert during the daytime hours but not as early as morning types, or they might stay awake later than morning types but not as late as evening types.
To better understand the mechanisms linking chronotype and wages, the researchers proposed a theoretical framework that combines economic models related to human capital, social capital, and health capital. This framework suggests that an individual’s chronotype can influence their accumulation of these different types of capital, which subsequently impact their productivity and wages.
The data used for the study come from a population-based cohort survey, known as the Northern Finland Birth Cohort 1966, allowing for a robust analysis of the links between chronotype, various forms of capital, and wages. Human capital was assessed through factors such as work experience and educational attainment, health capital was measured through behaviors like smoking and sleep patterns, and social capital was measured by analyzing trust and prosocial behavior. The final sample included 2,231 men and 2,789 women.
“My coauthors and I have worked on similar types of Behavioral Economics research, looking at the relationship between biological and/or psychological characteristics and economic outcomes,” said study author Andrew Conlin, a postdoctoral researcher at the Aalto University School of Business
“Given the unique data available in the Northern Finland Birth Cohort 1966, we thought we could contribute to the literature on the economic consequences of sleep. Using wages as the main outcome measure in this paper builds on a previous paper we published on the relationship between chronotype and self-assessed work ability.”
The researchers found that having an evening chronotype had indirect effects on wages. In other words, having an evening chronotype isn’t directly related to lower wages, but it is related to other factors that are associated with earning less money.
The biggest impact on wages came from health capital. For example, evening chronotypes tended to engage in unhealthy behaviors more often, such as being less physically active, smoking, and consuming more alcohol. They also were more likely to experience poor sleep outcomes, such as insomnia and sleeping less than 7 hour per night. The researchers showed that these factors together can explain why evening chronotypes might earn less money than morning chronotypes.
“Sleep matters,” Conlin told PsyPost. “That’s not surprising, we all know that. But we try to show potential mechanisms by which sleep is related to wages. Being an evening-chronotype person (an ‘owl’) seems to be associated with higher rates of poor health outcomes, which in turn are associated with lower wages.”
But the study, like all research, includes some caveats. The participants’ chronotype was assessed at one specific point in time when they were 46 years old. While the study can confidently draw conclusions about how being an evening person at age 46 is associated with work productivity, it cannot prove causal effects.
“The major caveat is that we can only show an indirect association between chronotype and wages; we are unable to make any claims about evening chronotype causing lower wages or causing poor health outcomes (think of the line ‘correlation is not causation’),” Conlin explained. “We were unable to use analysis methods that would have allowed us to test for such causation.”
“I think further research on the causal mechanisms would be very informative. Does a mismatch between chronotype and work schedule really cause lower productivity? Why is evening chronotype associated with poorer health outcomes – is there a common underlying biological factor?”
The study, “The association between chronotype and wages at mid-age“, was authored by Andrew Conlin, Iiro Nerg, Leena Ala-Mursula, Tapio Räihä, and Marko Korhonen.