Headache Impact of Chronic and Episodic Migraine: Results From the American Migraine Prevalence and Prevention Study
Authors: Buse Dawn , Manack Aubrey , Serrano Daniel , Reed Michael , Varon Sepideh , Turkel Catherine , Lipton Richard 
Published: November 2011

Background.— The Headache Impact Test‐6 (HIT‐6) has been demonstrated to be a reliable and valid measure that assesses the impact of headaches on the lives of persons with migraine. Originally used in studies of episodic migraine (EM), HIT‐6 is finding increasing applications in chronic migraine (CM) research.

Objectives.— (1) To examine the headache‐impact on persons with migraine (EM and CM) using HIT‐6 in a large population sample; (2) to identify predictors of headache‐impact in this sample; (3) to assess the magnitude of effect for significant predictors of headache‐impact in this sample.

Methods.— The American Migraine Prevalence and Prevention study is a longitudinal, population‐based study that collected data from persons with severe headache from 2004 to 2009 through annual, mailed surveys. Respondents to the 2009 survey who met International Classification of Headache Disorders 2 criteria for migraine reported at least 1 headache in the preceding year, and completed the HIT‐6 questionnaire were included in the present analysis. Persons with migraine were categorized as EM (average <15 headache days per month) or CM (average ≥15 headache days per month). Predictors of headache‐impact examined include: sociodemographics; headache days per month; a composite migraine symptom severity score (MSS); an average pain severity rating during the most recent long‐duration headache; depression; and anxiety. HIT‐6 scores were analyzed both as continuous sum scores and using the standard, validated categories: no impact; some impact; substantial impact; and severe impact. Group contrasts were based on descriptive statistics along with linear regression models. Multiple imputation techniques were used to manage missing data.

Results.— There were 7169 eligible respondents (CM = 373, EM = 6554). HIT‐6 scores were normally distributed. After converting sum HIT‐6 scores to the standard categories, those with CM were significantly more likely to experience “severe” headache impact (72.9% vs 42.3%) and had higher odds of greater adverse headache impact compared with persons with EM (OR = 3.5, 95% CI = 2.77‐4.41, P < .0001). Significant predictors of adverse headache impact in both groups included younger age, higher MSS score, higher average long‐duration headache pain severity rating, and depression. Lower annual household income, anxiety, and higher standardized headache day frequency predicted adverse headache impact in EM but not CM. With few exceptions, gender, race, and body mass index did not significantly predict adverse headache impact. Finally, rates of depression were more than double among persons with CM (CM = 25.2%, EM = 10.0%), and rates of anxiety were nearly triple (CM = 23.6%, EM = 8.5%).

Conclusions.— This work further establishes HIT‐6 as a useful instrument for characterizing CM and understanding the increased disease related burden. Persons with CM had significantly higher odds of greater adverse headache impact, when compared with EM. Predictors of greater headache impact for both groups included higher MSS scores, higher average headache pain severity, and depression. Additional predictors unique to EM included higher average household income, younger age, higher standardized headache day frequency, and anxiety. This finding may be related to differences in sample size and power. Further exploration is warranted.