Table 1.
Characteristics of participants in the OPPERA prospective cohort study (n = 2,410) and nested case-control study (n = 439)
| Prospective cohort study | Nested case-control study | ||||
|---|---|---|---|---|---|
|
| |||||
| Number of subjects (column %) | Number of QHUs per person (median) | TMD incidence rate* (% of people per year) (95% CI) | TMD cases: number of subjects (column %) | TMD-free controls: number of subjects (column %) | |
| All subjects | 2410 (100.0) | 10 | 2.8 (2.4, 3.2) | 248 (100.0) | 191 (100.0) |
| Age (years) | |||||
| 18–24 | 1266 (52.5) | 10 | 2.1 (1.7, 2.7) | 107 (43.2) | 92 (48.2) |
| 25–34 | 654 (27.1) | 11 | 2.9 (2.3, 3.8) | 76 (30.7) | 49 (25.7) |
| 35–44 | 490 (20.3) | 9 | 3.2 (2.4, 4.3) | 65 (26.2) | 50 (26.2) |
| Gender | |||||
| Male | 967 (40.1) | 9 | 2.2 (1.7, 2.8) | 87 (35.1) | 69 (36.1) |
| Female | 1443 (59.9) | 10 | 2.8 (2.4, 3.4) | 161 (64.9) | 122 (63.9) |
| Race-ethnicity | |||||
| White | 1324 (54.9) | 11 | 2.5 (2.0, 3.1) | 135 (54.4) | 99 (51.8) |
| African-American | 627 (26.0) | 8 | 3.4 (2.5, 4.4) | 79 (31.9) | 47 (24.6) |
| Asian | 228 (9.5) | 10 | 1.1 (0.5, 2.1) | 9 (3.6) | 24 (12.6) |
| Hispanic | 157 (6.5) | 10 | 2.2 (1.3, 3.8) | 18 (7.3) | 17 (8.9) |
| Other | 74 (3.1) | 11 | 2.7 (1.3, 5.7) | 7 (2.8) | 4 (2.1) |
| Headache classification at baseline | |||||
| No/unclassified headache | 839 (34.8) | 10 | 2.1 (1.6, 2.8) | 75 (30.2) | 62 (32.5) |
| TTH | 1310 (54.4) | 10 | 2.6 (2.1, 3.2) | 129 (52.0) | 109 (57.1) |
| Migraine | 248 (10.3) | 10 | 3.7 (2.6, 5.3) | 40 (16.1) | 16 (8.4) |
| Mixed headache | 13 (0.5) | 12 | 8.4 (3.1, 22.5) | 4 (1.6) | 4 (2.1) |
| Headache frequency at baseline | |||||
| 0 headache per month | 1117 (46.4) | 10 | 2.1 (1.6, 2.6) | 94 (37.9) | 90 (47.1) |
| 1 headache per month | 610 (25.3) | 11 | 2.2 (1.6, 3.0) | 49 (19.8) | 48 (25.1) |
| 2 headache per month | 367 (15.2) | 10 | 3.2 (2.3, 4.4) | 46 (18.6) | 30 (15.7) |
| 3 headache per month | 173 (7.2) | 10 | 3.6 (2.3, 5.7) | 25 (10.1) | 12 (6.3) |
| 4 headaches per month | 143 (5.9) | 8 | 6.0 (4.0, 8.9) | 34 (13.7) | 11 (5.8) |
Abbreviations: TTH = tension-type headache, QHU = quarterly health update, TMD = temporomandibular disorder, 95% CI = 95% confidence interval.
*
TMD incidence rate is computed using Poisson regression adjusted for study site (4 categories).