Stress, Sleep, and Allergy

Abstract: Allergic diseases have recently increased dramatically in the western world, now affecting about 30% of the Swedish population. The reasons for this increase are unclear, but some of the suspects are behavioral factors, such as stress and sleep. Problems with stress are also common today, and stress may change the set-points for the functioning of the body, for instance in the immune system. Sleep, on the other hand, is important for recuperation, and disturbed sleep acts a stressor in itself. Allergic patients often report stressful situations to cause allergic symptom exacerbations, and experience increased fatigue and disturbed sleep, especially when exposed to allergen. However, most aspects of the relations between stress, sleep, and allergy are still obscure. Therefore, this thesis aimed at increasing the understanding of these links. The thesis is based on three studies. The first is a quasi-experimental study of medical students with or without atopy, who were observed at two occasions, i.e. during a calmer study period and during a potentially stressful examination period (papers I & II). Assessments included blood sampling, lung function testing, and questionnaires and diaries on allergic and psychological symptoms and sleep. The results show that both atopic and non-atopic students increased ratings of stress and negative mood, had altered sleep patterns and changes in immune parameters, e.g. a marked increase in regulatory T-cells, during examination. Atopic participants also showed specific responses to stress, such as a shift towards T-helper 2 dominance, increased anxiety and disturbed sleep. Despite these changes, allergic symptoms were not affected. Paper III is based on a prospective epidemiological study, using parent report questionnaire data on aspects of disturbed sleep and allergy from the Twin Study of Child and Adolescent Development (TCHAD). Controlling for confounding effects of several factors, including gender, birth weight, and socioeconomic status, results from this study show that being overtired in childhood (age 8-9) predicts development of rhinitis in adolescence (age 13-14), but also that having asthma in childhood is predictive of becoming overtired in adolescence. Controlling for gender only, it also replicates findings from cross sectional studies of associations between allergy and disturbed sleep. The findings from paper I-III suggest that treatment of sleeping problems that are comorbid with e.g. allergies is an important issue. Therefore, paper IV is a randomized controlled trial of the efficacy of a CBT-based self-help treatment for insomnia with comorbid problems, including allergy. Assessments with questionnaires and sleep diaries took place at pre-treatment, post-treatment and three-month follow-up. The study shows that participants in the treatment groups display much improved sleep, and that the sleep of allergic individuals improved to the same extent as that of non-allergic individuals, despite co-existing allergic symptoms. In conclusion, stress is involved in allergy relevant immune changes, and the cumulative negative effects of stress (i.e. allostatic load) seem to be increased in atopic individuals as compared to non-atopics. The results thus speak for stress as a co-factor in an allergic reaction when exposed to allergen. Aspects of disturbed sleep may be involved in the development of allergy and vice versa, but disturbed sleep, also in individuals with allergy, can be treated efficiently with a CBT-based self-help treatment. The results of the thesis confirm a link between stress, sleep, and allergy, and suggest future studies to test if successful treatment of stress and sleep may decrease symptom expression or even diminish the risk for developing allergic disease.