Elon Musk, the world’s richest man and new CEO of Twitter, made headlines this week as Twitter managers told some employees to work 12-hour shifts for seven days a week in a sprint to meet Musk’s new November goals for the company, according to internal communications reviewed by CNBC.
Musk has long been a proponent of working long hours. In 2018, when someone asked him how many hours of work a week it takes to change the world, Musk replied on Twitter that it “varies per person, but about 80 sustained, peaking above 100 at times.”
He’s not the only CEO who believes long hours are necessary to get good work done: one Harvard study following 27 CEOs found they worked an average of 62.5 hours a week.
Unfortunately, lots of non-CEOs are working long hours, too. One Gallup poll found that half of all full-time US workers say they typically work more than 40 hours per week, and 18% said they were working more than 60 hours a week.
Last year, junior analysts at Goldman Sachs surveyed themselves about their hours and working conditions, finding they worked 95-hour weeks. As one anonymous junior banker put it in the survey, “There was a point where I was not eating, showering or doing anything else other than working from morning until after midnight.”
But according to science, there’s a clear point of diminishing returns at which working extra hours won’t actually make a difference at your job but will certainly wreak long-term damage on your body.
Here’s the research behind what actually happens to your body and brain after working more than 40 hours a week.
1. Your risk of dying from a stroke or heart attack goes up
Working too long can be a serious, and sometimes even fatal, health hazard.
According to a 2021 global study by the World Health Organisation and the International Labour Organisation, working long hours (which the study defined as more than 55 per week) caused 745,000 deaths from cardiovascular diseases in 2016 alone. Working 55 hours or more a week was associated with a 35% higher risk of stroke and a 17% higher risk of dying from heart disease, compared with working 35 to 40 hours a week.
“Long working hours can directly cause a cardiovascular disease event by increasing stress that damages cells in the brain and the heart,” Frank Pega, a WHO technical officer and the lead author of the paper, tells HuffPost. “They can also indirectly cause such disease events by triggering risky behavioural responses, such as less physical exercise, a less nutritious diet, or less sleeping time.”
His advice to those stuck working more than 40 hours a week? Organise with your co-workers and management for better working conditions.
“Workers and employers can enshrine healthy working hours in collective bargaining agreements,” Pega says. “Workers, governments and employers also all have a role to play in monitoring working hours against adherence to healthy limits.”
2. Your risk of getting injured on the job goes up
Working long hours also puts you at a greater risk of getting physically hurt while working.
In one study that looked at 110,236 job records from 1987 to 2000 using national longitudinal surveys, working at least 12 hours per day was associated with a 37% increased hazard rate, while working at least 60 hours per week was associated with a 23% increased hazard rate.
3. Your mental health worsens
When you keep sacrificing your need to rest in order to keep working, it can take a toll on your psyche.
One 2020 study published in the journal PLOS One looked at Korean workers in their 20s and 30s who worked from 31 to over 60 hours a week. The researchers found that the longer these employees worked, the higher levels of stress, depression and suicidal ideation they faced.
4. Your sleep suffers
When you’re staying up late to meet a boss’ deadline, your sleep pays the price.
In a review of 200 studies from 1998 to 2018, researchers writing in the International Journal of Environmental Research and Public Health concluded that “Short sleep duration... is the problem to be most concerned about with regard to long working hours,” citing how people who worked between 50-60 hours weekly in the studies were dealing with greater fatigue, worse cognitive function, more work injuries and mental health issues.
That’s because sleep is critical for our wellbeing. When you get less than six hours of sleep a night, you’re not just going to be grumpy at work the next day. Multiple studies have found that you will get more distracted, anxious, irritable and susceptible to impulsively taking bigger risks.
5. You actually stop being good at your job
The fact is, working longer hours doesn’t lead to better work.
University of California, Berkeley, management professor Morten Hansen conducted a five-year survey of 5,000 employees and managers across industries. He found that working between 30 and 50 hours can improve someone’s performance, but that if they work more than 50 hours, their job performance starts to plateau. And if they work more than 65 hours a week, their performance sharply drops off.
“Yes, you need to work hard (about 50 hours per week in my dataset), but that’s completely different from saying you need to work harder than others to rise to the top,” Hansen wrote on his website.
His findings are similar to what Stanford economist John Pencavel concluded about the productivity of munitions plant workers during World War I. These factory employees did repetitive tasks each shift and were asked to do between 60 to more than 100 hours of work a week.
Using the British Health of Munition Workers Committee’s analysis of their hours, Pencaval found that factory employees could increase their output if they worked up to 49 hours per week. But after that, working harder paid off less and less, and the chances of injury increased.
“Employees at work for a long time may experience fatigue or stress that not only reduces his or her productivity but also increases the probability of errors, accidents, and sickness that impose costs on the employer,” Pencavel concluded.
The bottom line for businesses? Asking an employee to work longer does not necessarily lead to better results. But it will certainly risk their health.