Insight

Chronic insomnia is a risk factor for asthma in adults
Katrina Mountfort, Senior Medical Writer, Touch Medical Media, UK
Matthew Goodwin, Respiratory Business Unit Director, Touch Medical Media, UK
Insights into the Nord-Trøndelag Health Study (HUNT), discussed at the ATS Annual Meeting, Washington DC, May 19–24, 2017

Asthma is one of the largest long-term health problems worldwide – it is estimated that more than 300 million people worldwide have asthma1 – and its incidence is increasing because of the effect of a wide number of environmental and lifestyle risk factors. As well as being potentially life-threatening in its own right, asthma has been associated with a range of serious illnesses including diabetes and heart disease.2 Many risk factors for asthma are known, including obesity, pollution, smoking, allergies, viral infections, family history, and exposure to certain dusts and chemicals. Depression and anxiety have also been linked to the development of asthma in adults.3

have also been linked to the development of asthma in adults.3 Earlier this year, a study published in the European Respiratory Journal identified a new risk factor for asthma in adults: chronic insomnia.4 The population-based cohort study examined data from the Nord-Trøndelag Health Study (HUNT), an ongoing health survey of the entire population over the age of 20 living in the county of Nord-Trøndelag, Norway, and involved 17, 927 participants aged between 20 and 65 who were free from asthma at the start of the study. The participants were asked to report how long it took them to fall asleep, how easy or difficult it was to stay asleep, and for an assessment of their sleep quality. They were also asked about asthma symptoms at the start and end of the study period. Odds ratios (OR) were calculated for the risk of incident asthma among those with insomnia compared to those without. The definition of insomnia included sleep initiation problems, sleep maintenance problems and poor sleep quality. Chronic insomnia was defined as one or more insomnia symptom(s) both at baseline and 10 years prior to the study. Incident asthma was assessed at the beginning and end of the study, approximately 11 years later.

Overall, sleep initiation problems, sleep maintenance problems and nonrestorative sleep were reported in 1%, 1% and 5% of participants, respectively. Analysis of the data showed that participants who reported any insomnia symptoms had a higher risk of developing asthma, compared to those without insomnia. The risk of asthma was increased by 18%, 30% and 70% for people with one, two and three insomnia symptoms, respectively, compared with those without symptoms (p<0.01). People who reported having trouble falling asleep often in the past month had a 65% higher risk of developing asthma during the following 11 years. This rose to 108% for those who had difficulty falling asleep almost every night. Participants with sleep maintenance problems such as waking up early and being unable to return to sleep often or almost every night had a 92% and 36% increased risk of asthma onset during the 11 years, respectively. Participants who reported poor sleep quality more than once a week had a 94% higher risk of developing asthma. The most significant finding, however, was in chronic insomnia: the risk of developing asthma was three-times higher (adjusted OR 3.16) in patients with chronic insomnia than those without.

Lead author Ben Brumpton of the Department of Public Health and General Practice, Norwegian University of Science and Technology said: "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,"

Sleep disorders are commonly reported in asthma patients5,6 – a recent study found that clinically significant insomnia was present in 37% of the participants with asthma7 – but until now the association between insomnia and the risk of developing asthma has rarely been investigated. In a previous analysis of the HUNT registry, insomnia was found to be a risk factor for asthma (OR 1.47), as well as a number of other physical and mental conditions.8 However, the study does not prove a cause-and-effect relationship between insomnia and asthma. Asthma is under-recognised within the general population,9 and it is possible that this study identified some individuals with undiagnosed asthma. However, this is unlikely to account for such a strong association between insomnia and asthma. Further prospective studies are needed to confirm this finding and to investigate whether treatment of insomnia can reduce the risk of asthma in these patients. In conclusion, this is a potentially important development in asthma prevention.

References

1. Global Initiative for Asthma, 2017 Appendix to GINA Report: Global Strategy for Asthma Management and Prevention, Available at: http://ginasthma.org/2017-online-appendix-global-strategy-for-asthma-management-and-prevention/ (accessed May 23, 2017).
2. Iribarren C, Tolstykh IV, Miller MK, et al., Adult asthma and risk of coronary heart disease, cerebrovascular disease, and heart failure: a prospective study of 2 matched cohorts, Am J Epidemiol, 2012;176:1014–24.
3. Brumpton BM, Leivseth L, Romundstad PR, et al., The joint association of anxiety, depression and obesity with incident asthma in adults: the HUNT study, Int J Epidemiol, 2013;42:1455–63.
4. Brumpton B, Mai XM, Langhammer A, et al., Prospective study of insomnia and incident asthma in adults: the HUNT study, Eur Respir J, 2017;49: DOI: 10.1183/13993003.01327-2016.
5. Cukic V, Lovre V, Dragisic D, Sleep disorders in patients with bronchial asthma, Mater Sociomed, 2011;23:235–7.
6. Janson C, De Backer W, Gislason T, et al., Increased prevalence of sleep disturbances and daytime sleepiness in subjects with bronchial asthma: a population study of young adults in three European countries, Eur Respir J, 1996;9:2132–8.
7. Luyster FS, Strollo PJ, Jr., Holguin F, et al., Association between insomnia and asthma burden in the Severe Asthma Research Program (SARP) III, CHEST, 2016;150:1242-50.
8. Sivertsen B, Lallukka T, Salo P, et al., Insomnia as a risk factor for ill health: results from the large population-based prospective HUNT Study in Norway, J Sleep Res, 2014;23:124–32.
9. Blakey JD, Zaidi S, Shaw DE, Defining and managing risk in asthma, Clin Exp Allergy, 2014;44:1023–32.