Objective  To explore the application of readmission ratio adjustment method in calculating the incidence rate of stroke among residents in Weifang city, Shandong province for estimating the first incidence rate of chronic diseases based on medical insurance database.

  Methods  The data on medical insurance reimbursement of hospitalizations due to ischemic and hemorrhagic stroke from 2016 through 2020 were collected from the Information System of Medical Insurance for urban and rural residents and that for urban employees in Weifang city. The gender-, age-, and medical insurance type-specific readmission rate coefficient (Ri, %) of different clearance periods (1 – 4 years) for the hospitalizations of the stroke inpatients during the period were calculated based on the data collected and then the calculated Ris were adopted to adjust the observed annual incidence rate of ischemic stroke and hemorrhagic stroke among the residents Weifang city from 2016 to 2020 with the clearance period of 1 to 4 years, respectively. The annual percentage change (APC) was analyzed by using the Joinpoint model to assess changing trend in the adjusted stroke incidence rates over the years. Furthermore, the gender-, age-, and medical insurance type-specific standardized incidence rates were also calculated and compared using Pearson chi-square test.

  Results  The overall Ri of clearance periods of 1 – 4 years for ischemic stroke hospitalizations in the city were 15.78%, 6.09%, 3.89%, and 2.86% and those for hemorrhagic stroke were 7.52%, 1.35%, 0.89%, and 0.83%, respectively. After the readmission rate adjustment and for the years from 2016 to 2020, the proportion of newly diagnosed cases among the yearly ischemic stroke inpatients were 71.58%, 71.49%, 70.09%, 70.77%, and 70.92%, and the proportion of newly diagnosed cases of hemorrhagic stroke was 89.39%, 89.37%, 88.92%, 88.92%, and 90.30%; the standardized incidence rates (1/ 100 000) of ischemic stroke were 542.41, 579.78, 514.82, and 531.96 and those of hemorrhagic stroke were 69.36, 69.78, 66.36, 65.16, and 65.55 for the populations in Weifang city, respectively. The Joinpoint analysis results showed that there was no significant change in change trend of ischemic stroke incidence from 2016 to 2020, but there was a downward trend in the incidence of hemorrhagic stroke (APC = – 1.78%, t = – 3.41, P < 0.05). During the 5-year period in the city, the standardized incidence rates of ischemic stroke and hemorrhagic stroke for male residents were 1.12 – 1.20 times and 1.26 – 1.41 times higher than those for female residents. The incidence rate of both ischemic stroke and hemorrhagic stroke increased with age. The incidence of ischemic stroke showed an accelerated increase at the age of 55 – 59, followed by a slowing down after the age of 70 – 74; while no obvious turning point was observed for the incidence of hemorrhagic stroke. For the residents with medical insurance in the city from 2016 to 2020, the incidence rates (1/ 100 000) of ischemic stroke were 515.47, 569.41, 562.87, 611.68, 690.49, and 515.47 and those of hemorrhagic stroke were 69.01, 69.78, 72.96, 73.6, and 79.66; for the employees with medical insurance, the incidence rates (1/ 100 000) of ischemic stroke were 468.55, 519.46, 483.71, 496.65, and 492.22 and those of hemorrhagic stroke were 51.25, 58.93, 57.75, 58.85, and 55.25/100000, respectively, indicating higher incidence rates of ischemic stroke and hemorrhagic stroke in the residents with medical insurance than those in the employees with medical insurance in all years (all P < 0.05).

  Conclusion  The readmission rate adjustment method could be used to estimate the incidence rate of stroke based on the medical insurance database. The analysis with this method reveals a relatively high incidence rate of stroke among the residents in Weifang city during 2016 – 2020, especially for that of ischemic stroke, however, there was no upward trend in the incidence rate over the period; the analysis also indicates that the males, the elderly, and the individuals with the medical insurance for urban and rural residents are key populations for stroke prevention in the city.