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Keywords:

  • epidemiology;
  • nested case–control design;
  • physical illness;
  • population study;
  • suicide risk

Abstract

Objective

To examine suicide risk in relation to physical illness across a broad range of illnesses, including hospitalization history, specific organ or system illness and comorbidity.

Design

A nested case–control study.

Setting

Data were retrieved from five Danish national registers.

Subjects

On the basis of the entire population of Denmark, this study included 27 262 suicide cases, and 468 007 live controls matched for sex and date of birth.

Main outcome measures

Risk of suicide was assessed using conditional logistic regression.

Results

In the study population, 63.5% of suicide cases and 44.5% of comparison controls had a history of hospitalization for physical illness. A physical illness significantly increased the risk of subsequent suicide (incidence rate ratios 2.13, 95% CI 2.07–2.18) with a substantially greater effect in women than in men (< 0.01). The elevated risk increased progressively with frequency and recency of hospitalization and was significant for diseases occurring in all organs or systems of the body. Comorbidity involving several organs or systems increased the risk substantially. The associated estimates were to some extent reduced but remained highly significant after adjustment for psychiatric history and socio-economic status. Taking into account both prevalence and adjusted effect size, physical illness accounted for 24.4%, 21.0% and 32.3% of population attributable risk for suicide in total, male and female populations, respectively.

Conclusions

Physical illness constitutes a significant risk factor for suicide independent of psychiatric and socio-economic factors. Clinicians treating physically ill patients should be aware of the risk, especially amongst those with multiple or recent hospitalizations, or multiple comorbidities.