Insomnia symptoms as risk factor for somatic disorders: An umbrella review of systematic reviews and meta-analyses

The objective of this umbrella review is to present a comprehensive summary of systematic reviews and meta-analyses on the longitudinal association between insomnia and the risk of developing somatic disorders. Pubmed, Medline, CINAHL, PsycInfo and PsycArticles were searched until 16 December 2022. Fourteen systematic reviews and meta-analyses met the inclusion criteria. Results suggest that insomnia symptoms (i.e. aspects of disturbed sleep continuity as a single symptom) convey a risk factor for cardiovascular diseases, hypertension and thyroid cancer. The presence of insomnia symptoms may also enhance the risk for obesity, cognitive decline and dementia-however, results are contradictory and not conclusive here. Results do not suggest an association between insomnia symptoms and mortality. No conclusions can be drawn regarding insomnia disorder because the reviews did not ensure a valid diagnosis. It remains unclear what proportion of participants with insomnia symptoms fulfil diagnostic criteria for insomnia disorder and/or suffer from an organic sleep disorder such as sleep-related breathing disorder. Moreover, most of the included reviews were assessed to have critically low confidence according to the AMSTAR-2 tool. Inconsistent definitions of insomnia and methodological unclarities further underline that results should be interpreted with caution. There is a need for future longitudinal studies that focus on a careful definition and differential diagnosis of both insomnia and the outcome.