People with schizophrenia often die at a considerably younger age than the rest of the population. Reasons for this include: late diagnosis and poor treatment of physical illnesses, metabolic side effects of antipsychotic medication, unhealthy lifestyle and high risk of suicide (reviewed by Laursen et al, 2014).

But how is higher mortality quantified? Previous systematic reviews and meta analyses have focused on standardised mortality ratios, predictors of increased mortality within populations with schizophrenia, and on relative risks of, or risk factors for cause-specific mortality. For non-experts, deciphering what these terms mean can be confusing and difficult to translate into health promoting policies.

In contrast, life expectancy can be used as a measure of mortality and health status in a population and enables comparisons of sub-populations. This allows researchers to quantify years of potential life lost to schizophrenia, a more direct measure of increased mortality. However, to date, life expectancy data has not been systematically reviewed. The subject of today’s blog is a recent systematic review and meta-analysis of literature that tries to address this issue by reporting life expectancy and potential life lost in people with schizophrenia (Hjorthøj et al, 2016).

Methods

• The search included articles up to July 2016 in the electronic databases MEDLINE, PsycINFO, EMBASE, Cinahl and Web of Science. No restrictions were placed on year of publication, geographical location or language
• Included studies reported data on years of potential life lost or life expectancy in patients diagnosed as having schizophrenia according to any version of ICD, DSM, or the Research Diagnostic criteria
• 11,830 unique entries were identified, 11,068 were excluded after reviewing title and abstract, full text articles were retrieved for 762 articles of which 13 papers comprising of 11 studies were eligible for inclusion
• All inhabited continents were represented with 2 studies from the UK, 5 Scandinavian, 1 Asian, 1 Australian, 1 African, 2 Canadian and 1 study from the USA
• 9 studies presented information on years of potential life lost and 6 on life expectancy. When just one study per area was included (to avoid duplication of patients). The total number of included patients was between 179,260 (small studies) and 247 603 (large studies).

Results

Years of potential life lost

• The overall weighted average for years of potential life lost to schizophrenia was 14.5 (95% CI 11.2 to 17.8)
• The number of years of potential life lost was greater for men 15.9 (95% CI 13.8 to 18.0) than women 13.6 (95% CI 11.4 to 15.8)
• When analysed for differences in geographical regions there were fewer years lost in the Asian study (12.8, 95%CI 10.7 to 15.0) and more years lost in the African study (27.7, 95% CI 25.5 to 25.9). Values did not differ substantially from the overall value for Australia, Europe or North America.

Life expectancy

• The overall weighted life expectancy for people with schizophrenia was 64.7 years (95% CI 61.1 to 71.3)
• For men, life expectancy was nearly 8 years shorter than for women at
  • Men 59.9 years (95% CI 55.5 to 64.3)
  • Women 67.6 years (95% CI 63.1 to 72.1)
• Life expectancy in the Asian study was lower (60.2, 95% CI 56.6 to 63.8) and for Africa was just 46.3 (95% CI 42.7 to 49.9)
• In the pre-2000 study, life expectancy was marginally lower (life expectancy estimated at birth; 56.2 for men, 66.1 for women).

Conclusions

The purpose of this study was to provide easy to understand measures of mortality in schizophrenia, including years of potential life lost and life expectancy. Using data from 11 studies, Hjorthøj et al (2016) showed that schizophrenia was associated with an average of 14.5 years of potential life lost. The loss was greater for men (15.9) than for women (13.6).  Life expectancy was greatly reduced in patients with schizophrenia, at 64.7 years (59.9 for men and 67.6 for women).

The presentation of this data by Hjorthøj et al (2016) and commentary by Galletly (2017) highlights the need for the development of effective interventions to address premature mortality in schizophrenia. Promoting healthy lifestyles in patients with schizophrenia is a difficult task, however there is also evidence that patients with schizophrenia receive sub optimal healthcare, with cardio-protective drugs such as antihypertensives and statins prescribed at lower rates (Lawrence et al, 2010) and high prescribing rates of antipsychotics with a high metabolic burden, despite clinical guidelines discouraging this (Goff et al, 2005).

Thus while clinicians should facilitate lifestyle improvements they should also focus on providing the best care for both the mental and physical health of patients with schizophrenia in order to bridge this mortality gap.

Strengths and limitations

The results of this study clearly show the increased mortality in patients with schizophrenia by presenting data which can be easily understood by non-experts. Another major strength was that even in studies with a higher risk of bias, the results were comparable.

However there are some limitations of this study:

• There were some issues with the included data. Included studies had overlapping geographical regions which meant that the lower estimates for years of potential life lost were used, which could mean that the true figure is higher. Some included studies did not reporting standard errors or confidence intervals, potentially leading to inaccurate results (both over- and under-estimated)
• The inclusion of just 1 study each from Asia, Africa and Australia means that the validity outside of Europe and North America is questionable. The limited number of studies representing some populations also made it difficult to account for differences in healthcare and lifestyle factors
• The inclusion of just 11 studies is a small pool of data from which to draw conclusions and also meant that subgroup analyses based on comorbid conditions and other risk factors were not possible.

Summary

• Data from this systematic review and meta-analysis showed that schizophrenia was associated with an average of 14.5 years of potential life lost. The loss was greater for men (15.9) than for women (13.6)
• This study also showed that life expectancy was greatly reduced in patients with schizophrenia at 64.7 years (59.9 for men and 67.6 for women)
• Studies that investigate mortality in schizophrenia should also report life expectancy and years of potential life lost, as this would enable a broader representation of countries and subgroups and more reliable data. Similarly this data should also be reported for other forms of severe mental illness
• Interventions to bridge this mortality gap should not just focus on lifestyle changes that patients can make, but should also encompass clinician led initiatives to improve mental and physical healthcare in these patients.

Links

Primary paper

Hjorthøj C, Stürup AE, McGrath JJ et al (2017). Years of potential life lost and life expectancy in schizophrenia: a systematic review and meta-analysis. Lancet Psychiatry. 2017 Apr;4(4):295-301. [PubMed Abstract]

Other references

Galletly CA. (2017) Premature death in schizophrenia: bridging the gap. Lancet Psychiatry. 2017 Apr;4(4):263-265

Goff DC, Cather C, Evins AE, et al (2005) Medical morbidity and mortality in schizophrenia: guidelines for psychiatrists. J Clin Psychiatry 2005; 66: 183. [PubMed abstract]

Laursen TM, Nordentoft M, Mortensen PB (2014). Excess early mortality in schizophrenia (PDF) .  Annu Rev Clin Psychol. 2014;10:425-48

Lawrence D, Kisely S, Pais J (2010) The epidemiology of excess mortality in people with mental illness. Can J Psychiatry 2010; 55: 752–60. [PubMed abstract]

Photo credits

• Judith E. Bell CC BY 2.0