Asthma and Sleep Disturbances : Associations to Comorbidities and Asthma Control

Abstract: This thesis aimed to investigate the associations between asthma control, asthma-related comorbidity, and sleep. Insomnia symptoms with asthma are common, and have commonly been explained by poor asthma control and asthma symptoms during the night, which affect most asthmatics to some degree. The impact of asthma-related comorbidity, however, is not fully known. Further aims were to analyze the effects of asthma control and comorbidities on asthma-related quality of life, and to analyze the effects of co-existing asthma and obstructive sleep apnea on objective sleep quality. Four different populations were investigated: the two large community-based cohorts GA2LEN (n=25,610) and LifeGene (n=23,875), a cohort of 369 young asthma patients (MIDAS), and a polysomnography study of 384 women (SHE).The GA2LEN study confirmed that insomnia symptoms remain a common problem among asthmatics. Poor asthma control and nasal congestion were important risk factors for insomnia symptoms. Smoking and obesity were other risk factors for insomnia symptoms among asthmatics.Asthma control, as assessed using the Asthma Control Test (ACT), was identified as the most important predictor of asthma-related quality of life in the MIDAS study. Combining the ACT score with data on insomnia, anxiety, and depression showed considerable additive effects of the conditions. In the SHE study, co-existing asthma and OSA were associated with worse objective sleep quality and more profound nocturnal hypoxemia than either of the conditions alone. The group with both asthma and OSA had the highest levels of the markers of systemic inflammation CRP and IL-6.  Uncontrolled asthma was a risk factor for all insomnia symptoms in the LifeGene study. Asthma-related comorbidity had a great impact on sleep quality; in particular, the combination of uncontrolled asthma and any comorbidity was unfavorable. Chronic rhinosinusitis was a risk factor for both insomnia symptoms and uncontrolled asthma. These findings have a high clinical relevance and underline the importance of structured evaluation of asthma control and attention to comorbidity in asthma care, as insomnia symptoms are common and affect quality of life. Optimizing asthma control is crucial for sleep quality, but treating asthma-related comorbidity must not be overlooked.