Insomnia and cardiorespiratory fitness in a middle-aged population : the SCAPIS pilot study

Background The relationship between insomnia and cardiorespiratory fitness (CRF), a well-established risk factor for cardiovascular disease, has not been extensively studied. We aimed to assess the independent association between insomnia and CRF in a population-based cohort of subjects aged 50 to 64 years. Methods Subjects participating in the Swedish CArdioPulmonary bioImaging Study (SCAPIS) pilot cohort (n = 603, men 47.9%) underwent a submaximal cycle ergometer test for estimation of maximal oxygen consumption (VO2max). Data on physical activity and sedentary time were collected via waist-worn accelerometers. An insomnia severity index score ≥ 10 was used to define insomnia. Results Insomnia was identified in 31.8% of the population. The VO2max was significantly lower in insomnia subjects compared with the non-insomnia group (31.2 ± 6.3 vs. 32.4 ± 6.5 ml* kg−1 *min−1, p = 0.028). There was no difference in objectively assessed physical activity or time spent sedentary between the groups. In a multivariate generalized linear model adjusting for confounders, an independent association between insomnia status and lower VO2max was found in men, but not in women (β = − 1.15 [95% CI − 2.23–− 0.06] and − 0.09 [− 1.09–0.92], p = 0.038 and 0.866, respectively). Conclusions We found a modest, but significant, association between insomnia and lower CRF in middle-aged men, but not in women. Our results suggest that insomnia may link to cardiovascular disease via reduced CRF. Insomnia may require a specific focus in the context of health campaigns addressing CRF. Electronic supplementary material The online version of this article (10.1007/s11325-018-1765-9) contains supplementary material, which is available to authorized users.