When counting sheep doesn’t work

Time has passed midnight. You are laying in bed, relaxed and calm, but you can not sleep. After a while, you start turning around, trying hard not to think of that you have to get up in 5 hours… 4 hours.. 3,5.. Sleep problems is actually not uncommon – as much as on of three Norwegians have now and then this problems in some way. One of them is insomnia, including problems falling asleep, nightly awakenings and sleepiness during the day. Insomnia has been found to be associated with an increased risk of coronary heart disease, but the underlying mechanisms for this association are largely unknown. However, it seems like physical condition may be a key factor. A recently published NTNU study aimed to investigate different insomnia symptoms in relation to physical condition, defined by VO_2peak, in a group of 3,489 healthy men and women living in Nord-Trøndelag.

VO_2peak was determined using a treadmill test, were the participants walked/ran until exhaustion. Participants reported how often they experienced sleep problems (difficulties falling asleep at night, repeated awakenings during the night, early awakenings without being able to go back to sleep, and daytime sleepiness) during the last three months. Physical activity level, resting heart rate, weight, height and blood pressure, lifestyle factors, chronic pain, anxiety and depression were also recorded from clinical examinations and questionnaires.

Insomnia was relatively common among the participants with 8% reporting problems falling asleep and waking up early, and as much as 16% reporting frequent awakenings. The interesting part is that participants reporting insomnia symptoms had a slightly lower VO2peak than participants without such symptoms. This trend was apparent for all the insomnia symptoms except for early awakenings. Also, an increasing number of insomnia symptoms were associated with decreasing VO2peak.

Linn B. Strand

In this study, insomnia and VO2peak were measured at the same point in time, thus it was not possible to determine the direction of the relationship. Individuals with insomnia may have been less likely to engage in physical activity, but it is also possible that a sedentary lifestyle could have lead to poorer quality of sleep. However, the authors accounted for physical activity level in their analysis and the reported association was largely independent of this. The participants also had to be healthy to be eligible to take the test and the findings may not reflect the association that would be seen in a less healthy population.Insomnia is a common and treatable condition, and increased focus on adverse health effects could be helpful in the prevention of cardiovascular disease. Future studies with a prospective design are needed to confirm the findings and to establish the direction of the relation of insomnia with VO_2peak. However, there is no doubt that exercise promotes energy and well-being – and, hopefully, better sleep.

Linn Beate Strand, researcher at Institute of Community Medicine, NTNU.