A chronic disease of the lungs' airways, asthma has been linked to obesity and pollution. Other risk factors include smoking, allergies, viral infections, family history, and exposure to certain dusts and chemicals.
Analyzing the link between asthma risk and insomnia
Sleep researcher and last author of the study Dr. Linn Beate Strand, from the Department of Public Health and General Practice at the Norwegian University of Science and Technology (NTNU) in Trondheim, explains the motivation of the study:
"Insomnia, defined as having difficulties initiating or maintaining sleep, or having poor sleep quality, is common among asthma patients, but whether insomnia patients have a higher risk of developing asthma at a later stage has not been thoroughly investigated."
Researchers examined data from the Nord-Trøndelag Health Study (HUNT), a continuous health survey of the entire population over the age of 20 living in the county of Nord-Trøndelag, Norway.
The team calculated the risk of incident asthma among adults with insomnia compared with their asthma-free counterparts. In total, the study examined 17,927 participants aged between 20 and 65.
Those with insomnia reported trouble falling asleep, trouble maintaining sleep, and poor quality of sleep - namely, "non-restorative" sleep.
Participants reported any insomnia symptoms at the beginning and at the end of the study, approximately 11 years later.
Chronic insomnia was defined as one or more insomnia symptoms at the beginning of the study, as well as 10 years prior to the study.
Asthma risk three times higher for those with chronic insomnia
Overall, the study showed that participants who reported insomnia symptoms had a higher risk of developing asthma, compared with their insomnia-free counterparts.
Those who reported having trouble falling asleep "often" in the past month had a 65 percent higher risk of developing asthma during the following 11 years. For those who had difficulty falling asleep "almost every night," the risk rose to 108 percent.
Additionally, those who reported trouble maintaining sleep - for example, waking up too early and not being able to resume sleep "often" or "almost every night" - had a 92 and 36 percent risk of asthma onset during the 11 years, respectively. Those who reported poor sleep quality "more than once a week" had a 94 percent higher risk of developing asthma.
Finally, those with chronic insomnia had a threefold higher risk of developing asthma compared with those who did not have insomnia.
The lead author of the study, Dr. Ben Brumpton, from the HUNT Research Centre, Department of Public Health and General Practice, NTNU, weighs in on the findings:
"A key finding in our study is that those people with chronic insomnia had more than three times the risk of developing asthma, compared to those without chronic insomnia, which suggests that any changes in the body due to insomnia may accumulate and result in more severe harmful effects on the airways."
"As insomnia is a manageable condition," Dr. Linn Beate Strand adds, "an increased focus on the adverse health effects of insomnia could be helpful in the prevention of asthma. Further prospective studies are required to confirm the findings of our study."