Income inequalities in stroke incidence and mortality: Trends in stroke-free and stroke-affected life years based on German health insurance data

Due to substantial improvements in prevention and therapy, stroke incidence and mortality rates have decreased during the last decades, but evidence is still lacking on whether all socioeconomic groups benefited equally and how the length of life affected by stroke developed over time. Our study investigates time trends in stroke-free life years and life years affected by stroke. Special emphasis is given to the question whether trends differ between income groups, leading to decreasing or increasing social inequalities. The analyses are based on claims data of a German statutory health insurance company of the two time periods 2006-2008 and 2014-2016. Income inequalities and time trends in incidence and mortality risks were estimated using multistate survival models. Trends in stroke-free life years and life years affected by stroke are analysed separately for income groups by applying multistate life table analyses. Stroke incidence and mortality risks decreased in men and women in all income groups. While stroke-free lifetime could be gained in men having higher incomes, improvements in mortality counterbalanced decreasing incidences, leading to increases in life years affected by stroke among men of the lower and higher income group. Among women, no significant changes in life years could be observed. Changes in stroke-affected life years occur among men in all income groups, but are more pronounced in the higher income group. However, irrespective of the income group the proportion of stroke-affected life years remains quite stable over time, pointing towards constant inequalities. Further research is needed on whether impairments due to stroke reduced over time and whether all socioeconomic groups are affected equally.