Impact of work hours on sleep quality: a non-linear and gendered disparity.

Purpose: Quality sleep is vital for good health. Although it is known that workhours affect sleep quality, it is not known at what point workhours begin to compromise sleep. Few studies consider workhours in the 'other job' (domestic and care work) or address reverse causality between sleep quality and how long people work. This study aimed to estimate the point at which weekly workhours harm sleep, among employed Australians aged 25-64.

Methods: Using Australian data (19,453 observations from 9,826 adults assessed 2013, 2017, and 2021), a maximum likelihood instrumental variable approach modelled the influence of domestic and care hours on workhours and then the effect of workhours on sleep. We tested for a non-linear pattern and a potential tipping point or limit at which sleep quality declines. Sleep quality scores were constructed from sleep duration (hours), quality rating, medications, and problems with onset.

Results: We estimated a population tipping point of 42 workhours per week, beyond which sleep quality deteriorated. Notably, women demonstrated a lower tipping point (36 h) beyond which their sleep quality deteriorated compared to men (47 h), likely linked to their greater care and domestic workhours in the home.

Conclusions: Our methods allowed us to specify the point at which weekly workhours were optimal for sleep quality and the point beyond which they become harmful. By considering unequal hours worked in care and domestic work, we were able to identify distinct gender differences in this relationship.