Family Impact of Migraine: Development of the Impact of Migraine on Partners and Adolescent Children (IMPAC) Scale

OBJECTIVE To describe the development of the Impact of Migraine on Partners and Adolescent Children (IMPAC) scale. BACKGROUND Although existing data and clinical experience suggest that the impact of migraine is pervasive and extends beyond the individual with migraine, no validated tools exist for assessing the impact of migraine on the family. METHODS The Chronic Migraine Epidemiology and Outcomes (CaMEO) Study is a longitudinal study of people with migraine in the United States. The Family Burden Module (FBM) of the CaMEO Study contained an item pool of 53 questions derived through literature review, clinician input, and patient focus groups pertaining to the following concepts: impact of migraine on family interpersonal relationships, activities, well-being, finances, and health-related quality of life. Respondents with migraine (ie, probands) were categorized into 4 groups based on household composition: migraine probands with partners/spouses and children (M-PC), migraine probands with partners/spouses only (M-P), migraine probands with child(ren) only (M-C), and migraine probands without a partner/spouse or child(ren) (M-O). The IMPAC scale was developed in 3 steps: (1) exploratory factor analysis and item reduction, (2) bifactor analysis, confirmatory factor analysis, and scoring, and (3) reliability and construct validity analyses. RESULTS The analysis of data from 13,064 respondents to the FBM meeting criteria for migraine yielded a 12-item IMPAC scale, with 4 items applying to all of the groups, 4 more items applying to the groups with partners (M-P and M-PC), and 4 additional items to the groups with children (M-C and M-PC). Item responses can be summed and converted into a scoring system assessing mild (<0.5 SD below mean; IMPAC scale Grade I), moderate (0.5 SD below to <0.5 SD above mean; Grade II), severe (0.5-<1.5 SD above mean; Grade III), and very severe (≥0.5 SD above mean; Grade IV) family impact. Test information curves relating to the IMPAC scale for each household type indicated adequate reliability across a large range of family burden severity (from ∼1 SD below to ∼3 SD above mean) and IMPAC scores showed moderate-to-large correlations with other validated tools (range, ± 0.38-0.52), providing support for construct validity. CONCLUSIONS We developed a questionnaire to assess family burden attributed to migraine that is brief, robust, and psychometrically sound, with a simple scoring algorithm that can be applied to various household compositions. This questionnaire may be valuable in research settings to provide quantifiable data on the impact of migraine on family dynamics and in clinical settings to facilitate conversations about family burden as a target and a motivation for better treatment.