Joint effects of educational attainment, type 2 diabetes and coexisting morbidity on disability pension: results from a longitudinal, nationwide, register-based study.

ABSTRACT

AIMS/HYPOTHESIS: High prevalence of coexisting morbidity in people with type 2 diabetes highlights the need to include interactions with education and comorbidity in the assessments of societal consequences of type 2 diabetes. The purpose of this study was to estimate the joint effects of education, type 2 diabetes and six frequent comorbidities. METHODS: Nationwide administrative register data on type 2 diabetes diagnosis, hospital admissions, education and disability pension were grouped at the individual level by means of a unique personal identification number. Included were all people (N = 2,281,599) in the age span of 40-59 years living in Denmark in the period 2005 to 2017, covering a total of 17,754,788 person-years. We used both Cox proportional hazards and Aalen additive hazards models to estimate relative and absolute joint effects of type 2 diabetes, educational attainment and six common comorbidities (CVD, cancer and cerebrovascular, respiratory, musculoskeletal and psychiatric diseases). We decomposed the joint effects of educational level, type 2 diabetes and comorbidities into main effects and the interaction effect, measured as extra cases of disability pension. RESULTS: Lower level of educational attainment, type 2 diabetes and comorbidities independently contributed to additional granted disability pensions. The joint number of cases of disability pension exceeded the sum of the three exposures, which is explained by a synergistic effect of lower educational level, type 2 diabetes and comorbidity. CONCLUSIONS/INTERPRETATION: In this population study, the joint effects of type 2 diabetes, lower education and comorbidity were associated with larger than additive rates of disability pension. An integrated approach that takes into account socioeconomic barriers to type 2 diabetes rehabilitation may slow down disease progression and increase the working ability of socially disadvantaged people.