Table 4 Poisson regression was used to evaluate baseline variables in HUNT2 and risk ratios (RRs) of headache status 22 years later in HUNT4 in persons who participated in all three surveys (n = 16,118). Precision of the estimates was assessed by 95% confidence interval (CIs). Reference group in all three headache status groups consisted of participants without headache in all three surveys (n = 6775)

Age 20–39 years

1.4

1.3–1.5

2.1

1.9–2.3

2.8

2.5–3.1

40–49 years

1.2

1.1–1.3

1.6

1.5–1.8

1.9

1.7–2.1

50 years or more (reference)

Gender (women vs. men)

1.5

1.4–1.5

1.7

1.6–1.9

2.3

2.1–2.5

Education (low vs. high)

1.0

1.0–1.1

1.2

1.0–1.4

1.1

1.0–1.2

 Migraine (yes vs. no)

2.5

2.5–2.6

3.8

3.5–4.1

3.7

3.6–3.9

 Migraine with aura (yes vs. no)

2.3

2.2–2.4

3.7

3.3–4.1

2.8

2.6–2.9

 Migraine without aura (yes vs. no)

2.5

2.4–2.5

3.7

3.3–4.0

3.0

2.8–3.1

 Non-migrainous headache (yes vs. no)

4.6

4.4–4.8

4.6

4.3–4.9

5.6

5.3–5.9

 Chronic headache without MOH³ (yes vs. no)

2.1

1.9–2.3

2.1

1.6–2.8

2.6

2.4–3.0

 MOH⁶ (yes vs. no)

2.3

2.1–2.5

4.1

2.5–6.8

3.3

2.9–2.7

 Chronic MSCs (yes vs. no)

1.4

1.4–1.5

1.6

1.5–1.7

2.1

2.0–2.2

 HADS A score (> 11 vs. < 7)⁷

1.5

1.4–1.7

1.8

1.5–2.1

2.1

1.9–2.3

 HADS D score (> 11 vs. < 7)⁷

1.5

1.3–1.7

1.4

1.1–1.9

2.1

1.9–2.5

 BMI⁸ (> 30 vs. < 25)

1.1

1.0–1.1

1.0

0.9–1.1

1.1

1.0–1.2

 Systolic BP (> 160 mmHg vs. < 140 mmHg)

1.0

1.0–1.2

0.7

0.5–0.8

0.6

0.5–0.8

 Smoking (daily or past vs. never)

1.1

1.0–1.1

1.1

1.1–1.2

1.2

1.1–1.2

 Days using alcohol per month (≥5 vs. 0)

0.8

0.7–0.9

1.0

0.8–1.1

0.7

0.7–0.8

 Inactive vs. high physical activity⁹

0.9

0.8–1.0

0.9

0.8–1.1

0.8

0.7–0.9