Patterns of sex-specific and age-specific risk indicators of suicide: a population-nested case-control study

Suicide is more common among males and in older age, but the understanding of sex-specific and age-specific risk indicators is limited.

To describe the sex-specific and age-specific prevalence of 25 suicide risk indicators in the year preceding suicide and estimate their associations with suicide.

Register-based population-nested case-control study in Sweden, 2009-2021, comprising 19 741 suicide cases and 197 296 general population controls matched by sex, age and county of residence. Death by suicide was collected from the cause of death register. 25 suicide risk indicators covering psychiatric history, somatic disorders, bereavement and sociodemographic factors in the previous year were collected from nationwide registers. Sex-specific and age-specific ORs of suicide for the presence/absence of each risk indicator in the prior year were estimated and complemented by risk differences.

Suicide cases were 70% male, 9% were aged 15-24 years, 29% 25-44 years, 36% 45-64 years and 26% 65+ years. In the year preceding suicide, the prevalence of most risk indicators was the lowest among males and people aged 65+ years. Most risk indicators also showed weaker 1-year associations with suicide in these groups. The median OR (IQR) of suicide across the 25 risk indicators was 14.6 (5.2, 29.1) in females versus 10.3 (4.3, 21.3) in males, and 17.4 (6.5, 28.9) in 24-44 year-olds versus 8.0 (3.6, 23.7) in people aged 65+years. Risk differences of suicide were larger in males across nearly all risk indicators.

There was considerable heterogeneity across sex and age groups, both in the prevalence of risk indicators preceding suicide and in their associations with suicide. Risk indicators were generally less common and displayed weaker associations with suicide on the relative risk scale among males and older people.

Suicides in males and older people may be harder to predict, as indicators are rarer. When males present with risk indicators, they generally have a higher absolute risk of suicide, making them important targets for prevention even when risk indicators do not cause suicide. Our findings underscore the importance of considering sex-specific and age-specific risk indicators for individualised suicide prediction and prevention.