The relationship between chronotype and intelligence: the importance of work timing

Péter P Ujma,Martin Dresler,Tanja G Baudson,Róbert Bódizs

doi:10.1038/s41598-020-62917-9

Abstract

Sleep-wake patterns show substantial biological determination, but they are also subject to individual choice and societal pressure. Some evidence suggests that high IQ is associated with later sleep patterns. However, it is unclear whether the relationship between IQ and later sleep is due to biological or social effects, such as the timing of working hours. We investigated the association between habitual sleep timing during work days and work-free days, working time and membership in Mensa, an organization of highly intelligent individuals (IQ ≥130) using a sample of 1,172 adults split between Mensa members and age- and sex-matched volunteers from a large web-based database. We found no difference in chronotype, and the later sleep timing of Mensa members on work days was fully accounted for by later work start times. Our results indicate that later sleep timing in those with higher IQs is not due to physiological differences, but rather due to later work schedules. Later working times and the resulting lower social jetlag may be one of the reasons why higher IQ is associated with lower prospective morbidity and mortality.

Highlights

Sleep-wake patterns show substantial biological determination, but they are subject to individual choice and societal pressure
We investigated differences in sleep timing on work days and weekends separately in order to separate the preferred chronotype from the effects of socially pressure on sleep-wake timing[1], and investigated the role of work schedules and additional lifestyle variables
Mensa members were characterized by later lights-off, sleep onset midsleep and wake-up times as well as shorter sleep latency, but only during work days

Summary

Introduction

Sleep-wake patterns show substantial biological determination, but they are subject to individual choice and societal pressure. Some evidence suggests that high IQ is associated with later sleep patterns It is unclear whether the relationship between IQ and later sleep is due to biological or social effects, such as the timing of working hours. Almost all previous research was conducted with adolescents or young adults, and most studies did not systematically measure work day and free day sleep-wake preferences and lifestyle factors which may influence this relationship. It is currently unknown whether the relationship between IQ and sleep-wake timing reflects individual differences in the biological chronotype or rather in social influences (such as different work and school schedules or differences in the use of stimulants or hypnotics). We investigated differences in sleep timing on work days and weekends separately in order to separate the preferred chronotype from the effects of socially pressure on sleep-wake timing[1], and investigated the role of work schedules and additional lifestyle variables

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Conclusion