Background
Methods
CaMEO study design and baseline survey
Ethics, consent and permissions
Study classifications of EM and CM
Questionnaire
Analyses
Results
Waves participated | Number of waves baseline headache status maintained | EM at Baseline, n (%)a; n = 15,313 | CM at Baseline, n (%)a; n = 1476 |
---|---|---|---|
Respondents participating in 1 wave only (EM, n = 4801; CM, n = 474) | |||
1 | 1 | 4801 (100) | 474 (100) |
Respondents participating in any 2 waves (EM, n = 2839; CM, n = 270) | |||
2 | 1 | 99 (3.5) | 159 (58.9) |
2 | 2 | 2740 (96.5) | 111 (41.1) |
Respondents participating in any 3 waves (EM, n = 2209; CM, n = 206) | |||
3 | 1 | 29 (1.3) | 98 (47.6) |
3 | 2 | 98 (4.4) | 53 (25.7) |
3 | 3 | 2082 (94.3) | 55 (26.7) |
Respondents participating in any 4 waves (EM, n = 2161; CM, n = 206) | |||
4 | 1 | 12 (0.6) | 87 (42.9) |
4 | 2 | 31 (1.4) | 34 (16.7) |
4 | 3 | 106 (4.9) | 34 (16.7) |
4 | 4 | 2012 (93.1) | 48 (23.6) |
Respondents participating all 5 waves (EM, n = 3303; CM, n = 323) | |||
5 | 1 | 21 (0.6) | 101 (31.3) |
5 | 2 | 35 (1.1) | 43 (13.3) |
5 | 3 | 46 (1.4) | 32 (9.9) |
5 | 4 | 165 (5) | 55 (17) |
5 | 5 | 3036 (91.9) | 92 (28.5) |
Random-effect variance parameter estimates
| |||||
Estimate
|
Standard Error
| ||||
Intercept | 0.82 | 0.01 | |||
Linear trend | 0.17 | 0.01 | |||
Quadratic trend | 0.09 | 0.01 | |||
Scale | 0.09 | 0.005 | |||
Fixed Effects
| |||||
Label
|
RR (95% CI)
a
|
DF
|
t
|
P
value
| |
Intercept |
3.98 (3.82–4.15)
| 16,788 | 66.53 | <0.0001 | |
Linear trend |
0.73 (0.72–0.75)
| 29,528 |
−28.49 | <0.0001 | |
Quadratic trend |
1.09 (1.06–1.11)
| 29,528 | 7.90 | <0.0001 | |
Cubic trend | 0.98 (0.97–1.00) | 29,528 |
−1.51 | 0.1318 | |
Headache status: CM vs. EM |
4.45 (4.3–4.59)
| 29,528 | 89.36 | <0.0001 | |
Headache status by linear trend interaction |
1.19 (1.13–1.26)
| 29,528 | 6.67 | <0.0001 | |
Headache status by quadratic trend interaction | 1.03 (0.98–1.08) | 29,528 | 1.26 | 0.2075 | |
Headache status by cubic trend interaction | 0.99 (0.95–1.03) | 29,528 |
−0.72 | 0.4710 |
Random-Effect Variance Parameter Estimates
| ||||||
Estimate
|
Standard Error
| |||||
Intercept | 0.52 | 0.01 | ||||
Linear trend | 0.15 | 0.01 | ||||
Quadratic trend | 0.09 | 0.01 | ||||
Scale | 0.08 | 0.005 | ||||
Fixed Effects
b
| ||||||
Label
|
RR (95% CI)
c
|
DF
|
t
|
P
value
| ||
Intercept |
1.16 (1.02–1.32)
| 16,650 | 2.28 | 0.0224 | ||
Sex: male vs. female |
0.9 (0.87–0.93)
| 16,650 |
−6.62 | <0.0001 | ||
Education: college graduate vs. non–college graduate |
0.96 (0.93–0.99)
| 16,650 |
−2.92 | 0.0035 | ||
Race: Caucasian vs. nonwhite |
1.19 (1.14–1.23)
| 16,650 | 8.78 | <0.0001 | ||
Household income: at or above national median vs. those below |
0.96 (0.94–0.99)
| 16,650 |
−2.42 | 0.0155 | ||
Comorbid count |
1.07 (1.05–1.09)
| 16,650 | 8.06 | <0.0001 | ||
Disability: MIDAS category TIC |
1.47 (1.46–1.49)
| 16,650 | 73.56 | <0.0001 | ||
Age at onset, y |
0.998 (0.997–0.999)
| 16,650 |
−3.20 | 0.0014 | ||
Duration of illness | 1.00 (1.00–1.00) | 16,650 | 0.83 | 0.4090 | ||
Linear trend |
0.74 (0.73–0.76)
| 29,304 |
−28.63 | <0.0001 | ||
Quadratic trend |
1.09 (1.07–1.11)
| 29,304 | 8.35 | <0.0001 | ||
Cubic trend | 0.99 (0.97–1.01) | 29,304 |
−1.34 | 0.1797 | ||
Headache status: CM vs. EM |
3.95 (3.84–4.07)
| 29,304 | 90.71 | <0.0001 | ||
Headache status by linear trend interaction |
1.26 (1.2–1.33)
| 29,304 | 9.34 | <0.0001 | ||
Headache status by quadratic trend interaction | 0.99 (0.94–1.03) | 29,304 |
−0.51 | 0.6434 | ||
Headache status by cubic trend interaction | 1.00 (0.96–1.04) | 29,304 |
−0.17 | 0.8627 |
Discussion
Implications for headache classification, diagnosis, and clinical practice
Implications for epidemiologic studies
Implications for clinical trial design
EM | CM | Negative Binomial Mixed-Model for Change From Baseline to Follow-Upe
| 1-Way ANOVA for Headache Frequency Change Score From Baseline to Follow-Up | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Time Contrast | Baseline | Follow-Upb
| Change Score | Baseline | Follow-Upb
| Change Score | Baseline Headache Status by Time Interaction Random-Effect Model-Based | Baseline Headache Status ANOVA Effect | |||||
Sample sizea
| μ1
| μ2
d
| μΔ
| n | μ1
| μ2
d
| μΔ
| Rawf
| RR |
P value | Mean Differencec
|
P value | |
Wave 1 vs. Wave 2 | 7759 | 3.98 | 4.14 | 0.16 | 829 | 19.77 | 14.61 | −5.16 | 0.71 | 0.67 (0.64 to 0.71) | <0.0001 | −5.32 (−5.69 to −4.95) | <0.0001 |
Wave 1 vs. Wave 5 | 4407 | 4.05 | 4.09 | 0.05 | 502 | 19.80 | 13.69 | −6.12 | 0.68 | 0.64 (0.59 to 0.69) | <0.0001 | −6.17 (−6.69 to −5.64) | <0.0001 |