Compared to the general population, people with severe mental illness, including schizophrenia, have higher levels of cardiovascular-related mortality, and that association has become stronger over recent decades, according to a new study publishing April 19 in PLOS Medicine by Amanda Lambert of the University of Birmingham, UK, and colleagues.

Previous research has identified higher incidence and mortality from cardiovascular disease in people with severe mental illness, but it was not known whether that association has changed over time. The new study involved a systemic review and meta-analysis of 108 previous studies including over 30 million participants in high-income countries, all aged 16 to 65 years of age at onset of psychiatric disorder.

The study found that, overall, the cardiovascular-related mortality rate for people with severe mental illness is about twice that of the general population (SMR 1.96, 95% CI: 1.61–2.39, p<0.001 for schizophrenia). People with schizophrenia are at greater risk than those with bipolar disorder, but the disparity exists across all types of severe mental illness and both cerebrovascular and cardiac mortality. For people with schizophrenia, the pooled hazard ratio/rate ratio for coronary heart disease was 1.8 (95% CI: 1.44–2.24, p<0.001) compared to controls and the pooled standardized mortality ratio for cerebrovascular accidents was 1.93 (95% CI: 1.63–2.28, p<0.001). For both schizophrenia and bipolar disorder, the association with cardiovascular-related mortality grew stronger between the 1970s and the 2000s. For instance, the hazard ratio/rate ratio for mortality from coronary heart disease in people with schizophrenia in the 1990s compared with the 1980s was 1.61 (95% CI: 1.14–2.28, p=0.014).

It was not possible to explore all possible confounders, such as smoking and obesity, and there was also considerable heterogeneity between the studies included in the meta-analysis. More research is needed to understand the reasons for the higher morbidity risk and to assess why it may have been worsening in recent decades.

"The increased relative risk of CVD diagnosis in more recent decades may be a result of disparity in smoking prevalence between people with SMI and the general population or increased use of antipsychotics. The changes since the 1990s approximately coincide with the release of newer, second-generation antipsychotics which are known to have worse metabolic effects," the authors say.

Lambert adds, "Our systematic review and meta-analysis of over 100 studies has confirmed a strong association between severe mental illness and cardiovascular disease which became stronger in the 1990s and 2000s."