Fig. 3

Age, period and cohort effects on migraine incidence rate by SDI quintiles. A Age effects are shown by the fitted longitudinal age curves of incidence rate (per 100,000 person-years) adjusted for period deviations. B Period effects are shown by the relative risk of incidence rate (incidence rate ratio) and computed as the ratio of age-specific rates from 1990–1994 to 2015–2019, with the referent cohort set at 2000–2004. C Cohort effects are shown by the relative risk of incidence rate and computed as the ratio of age-specific rates from the 1910 cohort to the 2010 cohort, with the referent cohort set at 1960. The dots and shaded areas denote incidence rates or rate ratios and their corresponding 95% CIs. SDI Socio-demographic Index