Table 2 Univariate risk factors for headache chronicity in patients with episodic migraine

Risk factorsOdds ratio95% CIp Value
Age, y, in quartiles
    <341.00Referent
    34–412.60.9–6.90.06
    42–513.01.2–7.90.02
    >514.41.7–11.10.002
Headache frequency, d
    0–41.00Referent
    5–97.62.2–26.10.001
    ≥10–1525.47.6–84.50.001
Duration of primary headache, y
    <141.00Referent
    14–220.70.3–1.50.50
    >221.91.0–3.40.04
Type of headache medication
    None1.00Referent
    Analgesics2.70.6–11.70.19
    Ergots2.90.4–23.00.40
    Triptans3.70.8–16.40.09
    Opioids4.40.3–59.70.27
Male1.50.8–2.90.21
Headache medication overuse23.411.4–48.40.001
>1 Headache medication used2.31.3–4.10.004
Regular use of preventive medication2.51.4–4.30.001