Mortality after hospital discharge for people with schizophrenia or bipolar disorder: retrospective study of linked English hospital episode statistics, 1999-2006

Principal findings

The risk of death for people recently discharged from inpatient psychiatric care in England is significantly higher than that in the general population. This excess risk was observed for patients with a diagnosis of schizophrenia and for those with a diagnosis of bipolar disorder. Our findings of a persistent mortality gap in England in patients discharged between 1999 and 2006 are similar to results recently published by Tiihonen et al on all cause mortality in people with schizophrenia over a similar time period in Finland.25 26 Additionally, our findings suggest that the differential mortality for people with schizophrenia has widened in some groups, a result that is similar to the findings from a systematic review by Saha et al in 2007.27 Much of the increase in mortality is attributable to deaths from natural causes, especially circulatory disease and respiratory disease. Our findings support the recommendation of Saha et al that “in light of the potential for second-generation antipsychotic medications to further adversely influence mortality rates . . . optimizing the general health of people with schizophrenia warrants urgent attention.”27

Strengths and weaknesses

Strengths of this study include its large size and the fact that it includes all records of discharges with a diagnosis of schizophrenia or bipolar disorder in the study period and is therefore nationally representative. By linkage to national mortality data we have included comprehensive information on mortality in these vulnerable groups, especially in the period after discharge from hospital when the risk of death is greatest.2 In addition, to the best of our knowledge, ours are the first published findings on trends in mortality over the past decade for people with bipolar disorder in England, a condition that shares some clinical and management characteristics with schizophrenia.28 These study characteristics aid the generalisability of our findings compared with previous studies in the UK, which have been limited to case registers within individual mental health trusts.29 30

To quantify the mortality gap and assess the trend in risk of mortality for people with schizophrenia or bipolar disorder, we calculated standardised mortality ratios, which take into account differences in the age structure of the cases, as well as changes in the underlying mortality rates of the general population. The widening gap in standardised mortality ratios alone could represent an absolute rise in mortality in the psychiatric population or a fall in mortality in the general population in conjunction with a smaller fall in mortality in the psychiatric population. Accordingly, we have presented rates for all causes of death after discharge compared with national mortality rates over the same period, which allowed us to compare trends in the absolute difference in mortality risk between the groups. Both figures—the standardised mortality ratios and the rates—show that the risk of mortality after discharge is substantial and that the gap in risk, whether calculated in relative or absolute terms, remains substantial. The standardised mortality ratios for schizophrenia and bipolar disorder towards the end of this observation period are similar to those recently reported from the South London and Maudsley Biomedical Research Centre psychiatric case register for 2007-9, which also found a similarly pronounced excess in younger patients.29

Potential limitations include the usual caveats concerning the use of routinely collected data, including information from hospital records and death certificates, which are not collected for research purposes.31 32 33 34 There are also caveats about the validity of a dichotomy between “natural” and “unnatural” categories of death, although the definitions of these categories from the ICD codes were standard.35 36 The case groups consisted of people who had been recently admitted to hospital with a principal diagnosis of a mental disorder during the period in question and cannot be said to represent all people with the disorders; they are likely to represent a more severely affected group at a period of higher risk. The severity of the disorders in the case groups might have changed over the monitoring period because of changes in admission policy. Keown et al found little evidence of any significant decrease in admissions for schizophrenia or bipolar disorder during this period,37 and our finding of minor reductions in discharges over the observation period compared with the increases in standardised mortality ratios suggests that the concentration of mortality risk in these patients admitted to hospital is unlikely to be the sole explanation for the widening mortality gap, although residual confounding with severity of illness cannot be excluded entirely.

Interpretation, unanswered questions, and need for further work

Schizophrenia and bipolar disorder are known to be associated with a higher risk of mortality.1 Over the past decade the contribution of natural causes to excess mortality in people with severe mental illness has been increasingly recognised, particularly the impact of coronary heart disease, stroke, and cancer.38 For example, Osborn and colleagues used information from the UK General Practice Research Database to follow up a community sample of people with severe mental illness and found that these people had a significantly increased risk of death from coronary heart disease and stroke compared with controls that was not wholly explained by antipsychotic medication, smoking, or social deprivation.39

While knowledge about the specific causes of death in severe mental illness are becoming clearer, the pathogenic mechanisms that culminate in higher than expected mortality from natural causes in people with mental disorder are little understood and likely to be complex.40 41 Mechanisms acting through the direct effects of symptoms of mental disorder are unlikely to have a large effect on mortality from natural causes, although they are likely to influence death from suicide and other unnatural causes.42 Premature deaths from natural causes are likely to be influenced by adverse lifestyle and social factors associated with the presence of mental illness—such as smoking, use of alcohol and illicit drugs, and exposure to poor housing and social conditions40 43—or the adverse effects of antipsychotic medication.44 45 It has been suggested, however, that these factors do not account for all the excess mortality,39 and there is an urgent need for more research to understand the contribution of the six leading global risk factors for mortality identified by WHO—namely, hypertension, smoking, raised glucose concentration, physical inactivity, overweight and obesity, and high cholesterol concentration—to excess mortality in people with severe mental illness, including schizophrenia and bipolar disorder.41

Our results reinforce the need for further research in the UK as the mortality gap has not decreased and is increasing in some groups, such as those aged over 65. These results have particular policy relevance in the context of the implementation of the new national mental health strategy in England. They strongly point to the need for continued action to target risk factors for both natural and unnatural causes of death, including known risk factors for circulatory and respiratory disease, particularly to lower the risk for these people in the year after discharge from hospital. It is encouraging that the government has recognised and prioritised the importance of preventing premature mortality in its recently published mental health strategy.22 A reduction of the gap is also a challenge for the forthcoming reorganisation of the NHS in England, for general practitioner commissioning, and for the reorganisation’s emphasis on an NHS driven by outcomes. The already widening mortality gap between people with schizophrenia or bipolar disorder and the general population, however, suggests that these policies might be challenging aspirations.