Epidemiology and clinical features of hypnic headache: A systematic review and meta-analysis

BACKGROUND: Hypnic headache is a neurological disorder characterized by recurrent headache attacks that occur exclusively during sleep, leading to awakening. Synthesizing the available epidemiological data might inform clinical decision-making. METHODS: We searched PubMed and Embase for observational studies on hypnic headache published between 1 May 2004, and 22 December 2022. Two investigators independently screened titles, abstracts, and full-text articles. We performed a random-effects meta-analysis with meta-regression to estimate the prevalence of hypnic headache and its clinical features based on epidemiologic data from population-based and clinic-based studies. RESULTS: Fourteen studies, one population-based and 13 clinic-based, met our eligibility criteria. The population-based study did not identify any people with hypnic headache. From 11 clinic-based studies, the pooled relative frequency of hypnic headache was 0.21% (95%CI, 0.13 to 0.35%; I2 = 87%) in adult patients evaluated for headache. The pooled mean age of onset was 60.5 years, with a slight female predisposition. Hypnic headache was typically bilateral (71%), pressing (73%), of moderate (38%) or severe (44%) pain intensity, and lasted about 115 minutes per attack. CONCLUSIONS: Our data should be cautiously interpreted due to between-study heterogeneity. The identified clinical presentation of hypnic headache can guide clinical diagnosis, in addition to the International Classification of Headache Disorders.