Natural subgroups of tension‐type headache: A population‐based study

To identify natural subtypes of tension-type headache (TTH) based on clinical characteristics. Tension-type headache is generally recognized as a bilateral, non-pulsating headache of mild-to-moderate intensity, with minimal accompanying symptoms. However, diverse symptomatology can be present with current diagnostic criteria. This study was a cross-sectional, secondary analysis of data previously collected from a nationwide population-based web survey data on headache and sleep, conducted in South Korea in October 2020. Categorical variables for TTH diagnostic criteria according to the third edition of the International Classification of Headache Disorders were analyzed to determine the natural subtypes of TTH. Of 3030 participants, 954 were identified with TTH. A four-class model was selected as optimal, revealing subtypes named "classic TTH," "severe TTH," "unilateral TTH," and "TTH with photophobia," comprising 413 (43.3%), 66 (6.9%), 376 (39.4%), and 99 (10.4%) individuals, respectively. The most common, "classic TTH," featured typical bilateral (413/413 [100.0%]), non-pulsatile headaches (220/413 [53.3%]) of mild-to-moderate intensity (400/413 [96.9%]). The "severe TTH" class exhibited the highest headache intensity (moderate headache intensity, 35/66 [53.0%]), and the greatest impact of headache (mean [± standard deviation, SD] six-item Headache Impact Test [HIT-6] score, 55.1 [6.0]). The "unilateral TTH" class was primarily mild headache intensity (277/376 [73.7%]) and lowest impact of headache (mean [SD] HIT-6 score 48.8 [8.3]). "TTH with photophobia" involved exclusive photophobia (99/99 [100%]) and was second to "severe TTH" in headache intensity (moderate intensity, 43/99 [43.4%]) and impact of headache (mean [SD] HIT-6 score 53.2 [8.1]). Of 954 total TTH participants, 56.7% were not "classic TTH" subtype and 51.4% had unilateral headache. We identified four TTH subgroups, each with unique clinical features, providing additional insights into TTH subtypes.