Working at this time may put you at greater risk of asthma

Bad news, professional night owls. A new study finds working the night shift for long periods is linked to an elevated risk of developing moderate to severe asthma.

This was found to be especially true among permanent night shift workers. So, it appears the longer you regularly burn the midnight oil, the higher your asthma risk. 

Working a night shift regularly may sound odd to traditional 9-5’ers, but it’s estimated that roughly one in five employees living in industrialized nations work a semi-regular night shift schedule. 

Now, regular night shift work will unavoidably screw up one’s circadian rhythm (the body clock that tells us to sleep at night and wake in the morning).

While most night shift workers will probably tell you they don’t mind sleeping during the day while everyone else works, a misaligned circadian rhythm has long been linked to a host of health problems such as cancer and cardiovascular issues.

For this project, researchers wanted to investigate if night shift work has any effect on asthma risk and severity as well. This study was a collaborative effort by both American and English researchers from several highly respected institutions (University of Oxford, Harvard Medical School).

The research team was also sure to analyze asthma rates among early birds and night owls working the night shift. Each person’s genetic likelihood of developing asthma was considered as well.

An enormous dataset containing lifestyle, medical, and employment information for 286,825 adults (ages 37-72) was used for this study. That data had been collected between 2007 and 2010. Among all those people, 83% worked traditional 9-5 hours, while 17% reported working in shifts. Within those shift-working participants, just over half (51%) were working night shifts.

Generally speaking, night shift workers tended to be men, drink less alcohol, sleep fewer hours, live in poorer neighborhoods, and were more likely to smoke. Perhaps more importantly, night shift workers were also found to have overall poorer health.

All told, roughly 5% of participants (14,238) developed asthma, with 4,783 of those cases being either moderate or severe.

After crunching the numbers and accounting for other risk factors (age, sex), researchers concluded that permanent night shift workers are 36% more likely to develop moderate to severe asthma in comparison to people working normal hours. Notably, people who are naturally early birds were found to be 55% more likely to develop asthma if they found themselves regularly working irregular hours.

Surprisingly, however, genetic asthma risk didn’t seem to influence asthma rates among shift workers.

The study’s authors caution that their research is ultimately observational, and thus can not confirm causation. Still, they theorize that it’s likely circadian misalignment caused by prolonged night shifts jumpstarts the onset of asthma. 

“Interestingly, chronotype does change with age, getting later through adolescence and then earlier as adults age, suggesting that older individuals might find it more difficult to adjust to night shift work than younger adults,” the study reads. “The public health implications of our findings are potentially far-reaching, since both shift work and asthma are common in the industrialised world.”

The full study can be found here, published in Thorax.