Long working hours killing 745,000 people a year, study finds May 17, 2021 Working more than 55 hours a week significantly increases the risk of stroke and deaths from heart disease, a new study has concluded. GENEVA — Working more than 55 hours a week significantly increases the risk of stroke and deaths from heart disease, a new study has concluded. The World Health Organization (WHO) and the International Labour Organization (ILO) said the research was the first global analysis of the impact of clocking up excessive hours on death and health generally. The study estimates long working hours caused 745,000 deaths worldwide in 2016, up by 29 percent since 2000.