Summary: Known variously as the mental load, invisible work, or the “second shift,” unpaid domestic labor imposes a hidden burden that wears down sleep and mental health. A comprehensive study from Osaka Metropolitan University quantifies the health cost of what researchers call “Time Poverty,” showing that total daily working hours—paid plus unpaid—are a major predictor of nonrestorative sleep and psychological distress, particularly for women.
Researchers analyzed responses from 3,959 healthy Japanese workers to measure the combined impact of income-generating work and unpaid care and domestic tasks. The findings reveal that while women often spend fewer hours in paid employment, they carry a heavier load of unpaid work, extending their total workday and increasing the risk of sleep problems and poor mental health.
Key Facts
- Participation gap: About 90% of women reported engaging in household chores, compared with approximately 40% of men.
- Nonrestorative sleep: Longer total working hours were linked to sleep that does not restore energy, producing chronic, “silent” exhaustion across both genders.
- Mental health predictor: High total working hours (paid + unpaid) were a stronger predictor of psychological distress in women than paid employment alone.
- Time Poverty: Defined as the state in which the combination of paid and unpaid responsibilities leaves little or no time for daily living, recovery, or rest.
- Policy blind spot: Current labor statistics typically track only paid, clocked-in hours and therefore overlook the unpaid labor that sustains households and communities.
Source: Osaka Metropolitan University
Mental load, invisible work, and the “extra shift” describe the same persistent problem: unpaid domestic work, mostly performed by women, that erodes sleep quality and mental wellbeing.
Domestic tasks—meal preparation, laundry, school drop-offs, medical appointments, and ongoing caregiving—are essential to daily life. Yet their value is often overlooked by institutions, employers, and public policy, which tend to measure only paid labor. When unpaid domestic work is added to paid employment, many people, especially women, face an extended and fragmented working day that prevents full recovery between tasks.
To explore these links, a team led by Professor Akiko Morimoto (Graduate School of Nursing) and Professor Naho Sugita (Graduate School of Economics) at Osaka Metropolitan University conducted a cross-sectional postal survey across five cities in Osaka Prefecture. From 12,446 recipients, the research analyzed 3,959 responses from healthy workers aged 40–64: 1,900 men and 2,059 women.
Participants reported average daily hours spent on paid work, housework, childcare, and caregiving. Sleep quality was assessed with a widely used single-item measure of nonrestorative sleep, and mental health was evaluated on a five-point Likert scale, which the researchers dichotomized into “very good/good/average” versus “poor/very poor.”
The analysis confirmed that although women often have shorter paid work hours than men, they spend substantially more time on unpaid domestic labor. That difference produces longer total working hours for women and a greater likelihood of fragmented days that prevent restorative rest. Receiver operating characteristic (ROC) analysis showed total daily working hours had greater predictive value for nonrestorative sleep and poor mental health than paid-work hours alone—especially among women.
After adjusting for confounders, longer total working hours were significantly associated with higher odds of nonrestorative sleep for both men and women and with higher odds of poor mental health among women. In short, the combination of paid and unpaid labor—rather than paid labor alone—better explains the sleep and mental health gap.
“For women, total daily working hours are a more important predictor of nonrestorative sleep and poor mental health than paid working hours alone,” said Professor Morimoto. Professor Sugita added, “Measuring total daily working hours and integrating those measures into policy and institutional design could reduce health disparities and advance gender equality.”
The study was published in Social Science & Medicine.
Key Questions Answered
A: No. The study shows that women’s total working day is often longer and more fragmented, even when paid hours are fewer. Fragmentation prevents deep recovery and leads to nonrestorative sleep—waking up as tired as when you went to bed.
A: Much of unpaid domestic labor is “invisible” cognitive work—scheduling, coordinating, planning, and multitasking. This persistent mental load creates a baseline stress that continues after paid work ends, raising the risk of psychological distress.
A: Researchers recommend quantifying unpaid domestic work in official data and policy discussions. Recognizing unpaid labor as legitimate work is the first step toward institutional changes—such as shorter workweeks, flexible schedules, and better childcare—that support recovery and health.
Editorial Notes
- This article was edited by a Neuroscience News editor.
- The full journal paper was reviewed for accuracy.
- Additional contextual information was provided by staff writers.
About this mental health research news
Author: Lee Scott
Source: Osaka Metropolitan University
Contact: Lee Scott – Osaka Metropolitan University
Image credit: Neuroscience News
Original Research (open access): “Associations of total daily working hours encompassing unpaid care and domestic work with nonrestorative sleep and mental health in middle-aged Japanese men and women: a cross-sectional study” by Akiko Morimoto, Hideaki Furuki, Naho Sugita, Risako Hayashi, and Nao Sonoda. DOI: 10.1016/j.socscimed.2026.118965
Abstract
Associations of total daily working hours encompassing unpaid care and domestic work with nonrestorative sleep and mental health in middle-aged Japanese men and women: a cross-sectional study
Objective
This study examined how total daily working hours that include unpaid care and domestic responsibilities relate to nonrestorative sleep and mental health among healthy, middle-aged Japanese men and women.
Methods
The cross-sectional analysis used postal survey data from 3,959 healthy, working adults aged 40–64. Respondents self-reported average daily hours spent on paid work, housework, childcare, and caregiving. Nonrestorative sleep was evaluated with a validated single-item measure; mental health was rated on a five-point scale and dichotomized for analysis.
Results
Women reported shorter paid-work hours but longer total daily working hours due to greater unpaid domestic involvement. Total daily working hours predicted nonrestorative sleep and poor mental health more accurately than paid-work hours alone, particularly for women. After controlling for confounders, longer total working hours were linked to higher odds of nonrestorative sleep in both sexes and to poor mental health among women.
Conclusions
Total daily working hours that include unpaid care and domestic tasks are an important determinant of sleep quality and mental health, with pronounced effects for women. Including unpaid labor in time-burden assessments and policy design could help reduce health inequalities and support gender-equitable solutions in work and social policy.