Low socioeconomic status based both on educational level and income has been associated with asthma and respiratory symptoms, but changes over time in these associations have rarely been studied. The aim was to study the associations between educational or income inequality and asthma and respiratory symptoms among women and men over a 20-year period in northern Sweden. The study was performed within the Obstructive Lung disease in Northern Sweden (OLIN) research program. Mailed questionnaire surveys...