New research shows just how stressful starting a new career as a doctor can be: stressful enough to have your DNA age six times faster than it normally would.
Scientists studying cellular ageing through DNA telomeres (the 'tips' of our chromosomes), which shrink as we get older, found that this natural shrinkage was happening at an accelerated rate among new doctors – the equivalent of six years' worth of shortening in just 12 months.
It's the first large, longitudinal study to look at the link between chronic stress and cell ageing, and the team behind the research says it could have implications for those in any high-pressure situation, from trainee soldiers to new parents.
"Research has implicated telomeres as an indicator of ageing and disease risk, but these longitudinal findings advance the possibility that telomere length can serve as a biomarker that tracks effects of stress," says one of the team, neuroscientist and psychiatrist Srijan Sen from the University of Michigan (U-M).
"It will be important to study how telomere changes play out in larger groups of medical trainees and in other groups of people subjected to specific prolonged stresses."
The researchers took DNA samples from 250 new doctors at the start and end of their first intern year. These were compared to samples from 84 U-M freshmen students. In addition, the team measured the participants' mental well-being and stress levels over time with the use of questionnaires throughout the year.
Besides "telomere attrition" being six times greater in the doctors, some other interesting findings came to light – for example, the longer hours the new doctors worked, the faster their telomeres shrank.
Working hours averaged out at 64.5 for a typical week, but some study participants went above and beyond that on a regular basis.
"The responses given by some of the interns in these surveys indicated that some were averaging more than 80 hours of work a week, and we found that those who routinely worked that many hours had most telomere attrition," says Sen.
"Those whose hours were at the lower end of the range had less telomere attrition."
So why do these shrinking telomeres matter? It doesn't necessarily mean that these doctors have just had six years knocked off their lives; however, this type of DNA ageing has been linked with a variety of health problems, including depression, cancer, cognitive decline and heart disease.
Telomeres essentially protect DNA chromosomes from damage – they've been compared to the plastic caps on the ends of shoelaces – and they also play an important role in helping the body grow and repair itself. The effectiveness of these 'caps' wanes over time as we get older and our telomeres shrink.
Telomere length varied even before the new doctors started their internships, the new study showed: those who scored high for neurotic personality traits, and those with more stressful family backgrounds were more likely to have shorter telomeres.
The researchers are hoping that the new study will help in a push for more regulated working hours for doctors at the start of their careers and beyond. It also shows the importance of managing stress and working hours whatever our role in life.
Next, the team wants to study a possible link between telomere length and shift work, which disrupts the body's natural circadian rhythms. In the meantime, the researchers are advising new doctors to get plenty of sleep and find ways to reduce stress levels.
"Our results suggest that reforms in intern training and work hours with a renewed focus on well-being is necessary to protect the health and viability of our physician workforce," says one of the researchers, psychiatrist Kathryn Ridout from U-M.
The research has been published in Biological Psychiatry.