Severe mental illness associated with increased CHD mortality
Patients with severe mental illness (SMI) are at increased risk of premature death. Sixty per cent of the excess mortality in patients with schizophrenia is attributable to natural causes1 and the standardised mortality ratio for cardiovascular disease has been reported to be in the region of 104 to 110. It is not known to what extent this is caused by lifestyle, antipsychotic medication or the condition itself.
A new study has found that the risk of cardiovascular mortality for patients with SMI may be greater than previously believed.
This historical cohort study identified 46,136 patients with SMI from the General Practice Research Database. Six control patients were selected at random for each patient with SMI. Stroke, CHD and cancer mortality data were collected over a 15-year period. The association of mortality with antipsychotic medication was also investigated.
The results were analysed in three age bands: 18-49 years, 50-75 years and >75 years.
The rate of CHD mortality was three times greater for patients in the youngest age band compared with the control group and almost double for patients with SMI aged 50-75 compared with the control patients. There was no increase in CHD mortality in patients with SMI aged over 75 years compared with the control group. The hazard ratios (HRs) were 3.22, 1.86 and 1.05 respectively.
For stroke deaths, the HRs in the three age bands were 2.53 (only six patients, result not significant), 1.89 and 1.34 respectively. Adjustment for smoking or social deprivation did not significantly change these results.
The only significant result for cancer deaths was an HR of 1.32 for respiratory tumours in patients with SMI aged 50-75, which lost significance after controlling for smoking and social deprivation.
Prescription of conventional antipsychotics was associated with an HR for CHD death of 2.12, compared with an HR of 1.38 for patients with SMI not prescribed any antipsychotics and a ratio of 0.86 for patients prescribed atypical antipsychotics. However, the apparent lack of risk with atypical antipsychotics may be misleading, as most of the prescriptions for these drugs occurred towards the end of the study period, and patients may not have been followed up for long enough to observe any increase in mortality.
This study suggests that the increased risk of cardiovascular mortality in patients with SMI is of greater magnitude than previously reported. The increased risk compared with patients without SMI reduces with increasing age, possibly because of a healthy survivor effect.
The data suggest that patients on high doses of conventional antipsychotics may be at particularly high risk of CHD mortality, although dose may simply be a marker of illness severity.
An audit of patients in our practice suggested that lifestyle factors contribute substantially to the increased risk: 52% of patients with SMI were smokers, 30% were obese (BMI >30) and 96% were inactive (below level 3 on the Allied Dunbar National Fitness Survey).
However, it is important to remember that there is as yet no evidence from intervention studies to support the provision of annual physical health reviews for these patients; given that this is a form of multiple risk factor intervention, the benefits are likely to be small.2
Osborn DPJ, Levy G, Nazareth I et al. Relative Risk of Cardiovascular and Cancer Mortality in People With Severe Mental Illness From the United Kingdom's General Practice Research Database. Arch Gen Psychiatry 2007; 64: 242-249Reviewer
Dr Phillip Bland