The impact of chronic migraine: The Chronic Migraine Epidemiology and Outcomes (CaMEO) Study methods and baseline results

Abstract

Background: Longitudinal migraine studies have rarely assessed headache frequency and disability variation over a year.

Methods: The Chronic Migraine Epidemiology and Outcomes (CaMEO) Study is a cross-sectional and longitudinal Internet study designed to characterize the course of episodic migraine (EM) and chronic migraine (CM). Participants were recruited from a Web-panel using quota sampling in an attempt to obtain a sample demographically similar to the US population. Participants who passed the screener were assessed every three months with the Core (baseline, six, and 12 months) and Snapshot (months three and nine) modules, which assessed headache frequency, headache-related disability, treatments, and treatment satisfaction. The Core also assessed resource use, health-related quality of life, and other features. One-time cross-sectional modules measured family burden, barriers to medical care, and comorbidities/endophenotypes.

Results: Of 489,537 invitees, we obtained 58,418 (11.9%) usable returns including 16,789 individuals who met ICHD-3 beta migraine criteria (EM (<15 headache days/mo): n = 15,313 (91.2%); CM (≥ 15 headache days/mo): n = 1476 (8.8%)). At baseline, all qualified respondents (n = 16,789) completed the Screener, Core, and Barriers to Care modules. Subsequent modules showed some attrition (Comorbidities/Endophenotypes, n = 12,810; Family Burden (Proband), n = 13,064; Family Burden (Partner), n = 4022; Family Burden (Child), n = 2140; Snapshot (three months), n = 9741; Core (six months), n = 7517; Snapshot (nine months), n = 6362; Core (12 months), n = 5915). A total of 3513 respondents (21.0%) completed all modules, and 3626 (EM: n = 3303 (21.6%); CM: n = 323 (21.9%)) completed all longitudinal assessments.

Conclusions: The CaMEO Study provides cross-sectional and longitudinal data that will contribute to our understanding of the course of migraine over one year and quantify variations in headache frequency, headache-related disability, comorbidities, treatments, and familial impact.

Trial registration: ClinicalTrials.gov NCT01648530.

Keywords: Migraine disorders; chronic migraine; epidemiology; episodic migraine; headache.

Figure 1.

Participant flow diagram. CM: chronic migraine; EM: episodic migraine; FBM: Family Burden Module; CaMEO: Chronic Migraine Epidemiology and Outcomes Study. ^aN = 22,365 respondents either abandoned the survey (<20% of the survey was complete and headache status could not be identified), were over-quota, or had unusable data, which left 58,418 with usable returns. ^bBaseline-sampling was quota based with the limit for the migraine sample defined as n = 17,000. Respondents who replied after quotas had been reached, but before initiation of the next sampling wave, were deemed over-quota and not included. Of the quota sample, n = 16,789 met the inclusion criteria: agreed to participate, screened positive for modified ICHD-3 beta migraine, completed initial surveys in a reasonable time (≥10 minutes), were 18 years old, were not missing headache frequency data, and reported consistent age and sex (of the 17,000 people in the migraine sample, as defined by the quotas, 211 (1.2%)) were removed during data cleaning (Table 2)). Migraine case rate was 28.7% (16,789/58,418). ^cBecause of the risk of potentially low response rates for the Family Burden Module, respondents who were considered to be over-quota for CaMEO were resampled for the Family Burden Module only. Data from these over-quota respondents were not used for any other module.

Figure 2.

Study design. N = number of returns for that module only, and does not represent a running total of participation in previous modules. Module completion dates are as follows. Stage 1: Screening, Wave 1 Core, and Barriers to Care, September 17–October 30, 2012. Stage 2: Comorbidities/Endophenotypes, October 10–December 17, 2012; at the conclusion of wave 4 and before start of wave 5, nonrespondents to the Comorbidities/Endophenotypes Module were resampled (August 19–October 3, 2013). Family Burden-Proband, November 14, 2012–January 28, 2013. Family Burden-Partner, November 30, 2012–October 30, 2013. Family Burden-Child, January 11–October 30, 2013; at conclusion of wave 3 and before wave 4, nonrespondents to the Family Burden Survey were resampled (Proband, April 22–September 4, 2013; Partner, May 7–October 30, 2013; Child: May 3–October 30, 2013). Stage 3: Wave 2 Snapshot, December 21, 2012–February 19, 2013. Wave 3 Core, March 20–May 15, 2013. Wave 4 Snapshot, June 20–August 19, 2013. Wave 5 Core, September 19–November 19, 2013. For Wave 1 Core, no cases could attrit; the total returns screening positive for migraine were n = 17,000 out of n = 58,629 (these cases plus the n = 10,044 who were over-quota and n = 12,110 who abandoned produce the total returns of n = 80,783); of these, n = 211 (1.2%) were removed during cleaning, resulting in a final sample of n = 16,789 qualified respondents. All five waves of longitudinal assessments were completed by n = 3626 of n = 16,789 (21.6%) respondents; four of five waves by n = 2364 (14.1%), three of five waves by n = 2415 (14.4%), two of five waves by n = 3109 (18.5%), and only one wave (i.e. baseline) by n = 5275 (31.4%).