To assess the socio-economic distribution of comorbid depression and diabetes among the Danish workforce using national registry data.
Using national registers, all eligible Danish adults aged 18-59 years on 1 January 1996 were followed until 31 December 2010. Diabetes status was obtained from the Danish National Diabetes Register and information on purchase of prescription antidepressants from the Register of Medicinal Product Statistics. Data were also obtained on people's occupational status and gross annual income. The people included in the study were stratified according to their highest occupational group during the study period. Annual incomes were adjusted to 2013 levels and, using the distribution of the study population's incomes, we stratified participants into income quintiles.
A total of 3 434 420 individuals met the inclusion criteria at baseline, with 98 006 developing diabetes during follow-up. There were 603 498 new prescriptions of antidepressants during follow-up; 19 849 (20.3%) among people with diabetes and 583 649 (17.5%) among those without. People with diabetes in all income quintiles (risk ratio 1.65; 95% CI 1.62-1.67) and all occupational groups (risk ratio 1.70; 95% CI 1.68- 1.73) had a significantly elevated risk compared with the general population. Risk ratios were significantly higher among the lowest occupational groups and income quintiles.
Our results provide robust data underlining the associations between diabetes, depression and socio-economic status. They highlight and encourage further focus on the issue of comorbid diabetes and depression, particularly among the most disadvantaged.