Geographic latitude and sleep duration: A population-based survey from the Tropic of Capricorn to the Antarctic Circle

ABSTRACT

The impact of latitude on sleep duration remains virtually unexplored, even though latitude exerts profound influences on daylight duration. Using Chile as a one-country model, we explored on the potential associations between sleep duration and latitude. Based on the 2nd Chilean Health Survey, we identified reported sleep data during spring of people living from north to south in Chilean cities, located between 18°29ʹS to 53°18ʹS (4329 km distance at same longitude). A total of n = 2493 participants were included (mean age 45.3 ± 18.4 years, 41.8% males). Mean sleep duration on workdays and weekends was 7.42 ± 1.71 h, and 7.91 ± 2.13 h, respectively, ranging from 7.91 ± 1.92 h in the north to 8.33 ± 1.89 h in the south, such that more northern latitudes (i.e., 18°29ʹS to 39°50ʹS) slept less compared to more southern latitudes (i.e., 51°43ʹS–53°18ʹ), even after controlling for age, gender, and socioeconomic status. In the logistic regression models, men residing at northern latitudes exhibited an odds ratio of 3.348 [95% CI: 1.905–5.882; p < 0.0001] for having shorter sleep on weekends than their southern counterparts. Latitude appears to strongly affect reported sleep patterns, leading to longer sleep duration with increasing latitude, particularly in men during weekends. Whether environmental factors such as photoperiod are causally involved in theses associations needs to be elucidated in future studies.

KEYWORDS:

• Circadian
• geography
• insomnia
• sleepiness
• sleep hours

Acknowlegdement

We thank the Chilean Health Ministry (MINSAL) who founded the 2nd National Health Survey 2009–2010, which was used for this study, and the FONDECYT project (#11130573) that supported the analysis.

Declaration Of interest

The authors have no conflict of interest to declare.

Funding

The Chilean Health Ministry (MINSAL) founded the 2nd National Health Survey 2009–2010 used for this study and the FONDECYT project (#11130573) that supported the analysis.

Additional information

Funding

The Chilean Health Ministry (MINSAL) founded the 2nd National Health Survey 2009–2010 used for this study and the FONDECYT project (#11130573) that supported the analysis.