Risk profiles before suicide mortality in patients with bipolar disorder across the lifespan

Abstract

Background: Studies examining age-stratified risk factors for suicide among individuals with bipolar disorder in different stages of life are scant, possibly because of the insufficient number of suicide cases.

Aim: This study investigated suicide mortality rates and risk profiles of suicide mortality stratified by five age groups in individuals with bipolar disorder.

Methods: This study identified patients with a diagnosis of bipolar disorder between January 1, 2000, and December 31, 2021, from Taiwan's National Health Insurance Research Database. The study population comprised 45,211 inpatients diagnosed with bipolar disorder, with 1,370 suicide cases during the study period. We calculated the standardized mortality ratio (SMR) of the bipolar cohort relative to the general population. In the age-stratified nested case-control study, risk set sampling was performed to match 1 suicide case with 10 living controls by age, sex, and the year of first diagnosis. The age-stratified risk associated with demographic characteristics, psychiatric and physical comorbidities was estimated using multivariable conditional logistic regression.

Results: The highest SMR (47.0) for suicide was observed in individuals with bipolar disorder aged <30 years. SMR decreased with age; patients aged >60 years had an SMR of 9.5. Among those younger than 40 years, a higher percentage of unemployment was noted among suicide cases than among controls. A significantly increased risk of the depressive phase of bipolar disorder was noted shortly before suicide mortality among patients with bipolar disorder in all age groups. Drug-induced and alcohol-induced mental disorders were associated with suicide and were highly prevalent in patients aged <30 years. Other forms of heart disease were identified in patients aged <40 years, and pneumonia was detected in the 50-59 years age group.

Conclusions: These findings aid the development of health-care intervention strategies for preventing suicide among patients with bipolar disorder in various stages of life.

Keywords: bipolar disorder; lifespan; nested case–control study; risk profile; suicide mortality.

Figure 1.

Incidence and standardized mortality ratio (SMR) of patients with bipolar disorder by age and sex. Error bars show 95% CI of incidence and SMR.

Figure 2.

Multivariable conditional logistic regression of adjusted risk ratios of psychiatric and physical comorbidities in a nested case–control study stratified by age. Variables from e-Table 4 in the Supplementary Material remained in the multivariable conditional logistic regression model with P < 0.01 after stepwise selection. *P < 0.01; **P < 0.001.