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 (VO2 max). 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 VO2 max 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 VO2 max 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.