unpaid work done by women
Women do most of the work that is unpaid1. This is, cooking, cleaning the house, caring for children. Therefore, the statistics that show that women's health deteriorate at lower week-working-hours than men, is pointing towards the fact that women already work more hours and they also work for-pay somewhere else. This effect has consequences in many different metrics, industries, and countries.
Work policies designed for the average will be biased towards men.