Effects of severe mental illness on survival of people with diabetes.

BACKGROUND People with mental health problems are more likely to die prematurely than the general population but no study has examined this in individuals with diabetes. AIMS To compare survival rates in people with diabetes with and without schizophrenia or bipolar disorder. METHOD A total of 43,992 people with diabetes were drawn from the QRESEARCH database population of over 9 million patients. Survival rates during the study period, between 1 April 2000 and 1 April 2005, and hazard ratios for deaths associated with schizophrenia and bipolar disorder were adjusted by age and gender and additionally for socioeconomic status, obesity, smoking and use of statins. RESULTS Among the participants, we identified 257 people diagnosed with schizophrenia, 159 with bipolar disorder and 14 with both conditions. Although crude survival rates did not show significant differences between the groups during the study period, people with schizophrenia or bipolar disorder and diabetes, compared with those with diabetes alone, had a significantly increased risk of death after adjusting for age and gender, with hazard ratios for schizophrenia of 1.84 (95% CI 1.42-2.40) and for bipolar disorder of 1.51 (95% CI 1.10-2.07). After adjusting for the other factors, hazard ratios were 1.52 (95 CI 1.17-1.97) for schizophrenia and 1.47 (95% CI 1.07-2.02) for bipolar disorder. CONCLUSIONS People with schizophrenia or bipolar disorder in addition to diabetes have a relatively higher mortality rate. This suggests that diabetes either progresses more rapidly or is more poorly controlled in these individuals, or that they have higher levels of comorbidity and so are more likely to die of other causes.