Fig 1. Age-specific rates of asthma in Italy by period of asthma onset and birth cohort:

A) Age-specific rates by year of onset: age at onset on x axis, with rates corresponding to same period connected by lines; B) Age-specific rates by birth cohort: age at onset on x axis, with rates corresponding to same cohorts connected by lines; C) Period-specific rates by age: year of onset on x axis, with rates corresponding to same age groups connected by lines; D) Cohort-specific rates by age: year of birth on x axis, with rates corresponding to same age groups connected by lines.