Risk factors for mortality after hospitalization for suicide attempt: results of 11-year follow-up study in Piedmont Region, Italy

Suicide attempters are at high risk of premature death, both for suicide and for non-suicidal causes [1‐13]. Mortality rates vary from 1.2 to 37.6% in studies covering a follow-up period of 1–32 years [1‐3, 5, 7, 9, 10, 12‐19]. The risk of death is highest within the first year after the episode of suicide attempt and remains elevated for many years afterwards [1, 2, 6, 7, 10, 11, 13, 16, 17, 20, 21].

The burden of suicide attempt is difficult to estimate due to underreporting and lack of standard reporting procedures in many countries. The prevalence of lifetime suicide attempt was estimated as 1.8% in 2001–2003 in Europe [22], and 0.3–4.2% in 2001–2007 worldwide [23‐25]. In more recent years, an increasing trends of suicide attempt rates have been reported in some countries [26‐30].

The identification of sociodemographic and clinical risk factors predicting premature mortality is of paramount importance to address high-risk subgroups and target them with appropriate health care and prevention interventions. A number of risk factors for mortality have been documented in prospective studies, i.e. male gender, older age, living alone, being single, lower education, income area/socioeconomic status, unemployment, retirement, violent method of suicide attempt and repetition of attempt [1‐7, 9, 11, 13‐18, 20, 31‐34]. Psychiatric disorders and physical illnesses co-occur commonly and represent a noteworthy risk factor for increased mortality among suicide attempters, particularly in the presence of both conditions [2, 4, 5, 21, 22, 28, 31, 35‐37]. Among psychiatric disorders, anxiety, depressive and bipolar disorder, schizophrenia, alcohol and drug abuse, and personality disorder are the most recognized co-existing diagnoses associated with mortality risk, and when co-occurring can significantly reduce the temporal interval from first episode of suicide attempt to death [3, 4, 6, 9, 13, 20, 21, 33, 37].

Most studies on risk factors for mortality following suicide attempt were conducted in North-Europe where the rates of suicidal behaviours are particularly high. Due to different prevalence rates and context, studies investigating the phenomenon in South-Europe are needed.

The aim of this study is to investigate risk factors and temporal span for mortality in a cohort of cases admitted to hospital or emergency department for suicide attempt between 2010 and 2020 in Piedmont, a North–West Italian Region with high rates of suicidal behaviour [38].

We conducted a cohort study by linking health and administrative data of the Piedmont Region following prospectively 1489 patients who were admitted to hospital or ED for suicide attempt between 2010 and 2020. To our knowledge, this is the first study to investigate risk factors for mortality in a cohort of hospitalized suicide attempters over 11-year span in Italy. Our study extends prior findings by adding new evidence from the South-European context. In this study, male gender, older age, high area deprivation index, single-parent family, comorbidity with mood disorders, malignant neoplasms and intracranial injury or skull fracture were predictors of all-cause death following the first hospital admission for attempted suicide. Older age, living in couples without children and single-parent family, being affected by malignant neoplasms and diabetes mellitus predicted natural-cause death, whereas gender and older age increased the risk of unnatural-cause death. The risk of death was highest during the first 12 months after suicide attempt, and remained elevated for many years afterwards.

The mean age at first episode of suicide attempt was in the range with previous studies [3, 17, 41, 42]. About one third of all suicide attempts occurred in adolescents and young adults, similarly to one fourth reported in a 9-year follow-up study in Belgium [43]. Consistently with prior studies, a greater proportion of younger females and older males attempted suicide [44, 45]. Our study also confirms earlier findings that psychiatric disorders and physical illnesses co-occur commonly in suicide attempters [3, 7, 21, 22, 24, 25, 28, 33, 35‐37, 46‐49].

During the observation period, 7.3% of subjects died, similar to previously observed 6.4% in Canadian and 8.7% in USA cohorts [9, 10], but lower than 12.1% reported in the Italian cohort by Pavarin and colleagues [16]. Although the risk for suicide and non-suicidal mortality persists for many years following the first episode, it is particularly pronounced shortly after the attempt episode [1‐3, 6, 7, 10‐13, 16, 17, 20, 21, 50]. In our study, 45% of deaths occurred in the first 12 months: this result points out that the period following the attempt episode is the most critical, and suggests that integrated and intense prevention and care interventions should be implemented in this period.

In the adjusted regression model, several characteristics emerged as significant predictors of mortality following suicide attempt. It is already well established that male gender is a significant predictor of mortality, particularly for suicide, among suicide attempters [1, 4‐7, 9, 16, 18, 20, 32, 33]. Consistently, also in our study, the survival time was significantly lower for males than females [1, 2, 4, 5, 33, 50]. This may be attributable to a higher tendency of males to use violent methods and their higher intention to die, a relevant risk factors for suicide particularly within the first months after the attempt [3, 5‐7, 13‐15, 18, 31, 34, 37, 42, 51]. Moreover, males in our cohort had more alcohol and drug related problems than female suicide attempters, a behaviour that may contribute to violent causes of death [3, 4, 6, 7, 20, 42, 51]. This result is similar to that observed in the Finnish cohort by Suominen and colleagues [4]. Moreover, in our study, a greater proportion of males was diagnosed with intracranial injury or skull fracture, conditions that may act as a proxy of violent suicide methods and therefore be linked to a higher risk of death for unnatural causes.

In agreement with earlier studies, the risk of death increased with the increase of age at the time of suicide attempt [1, 5‐7, 9, 16, 18, 20, 31‐33, 49], possibly due to higher prevalence of health problems in older patients [31, 35]. Indeed, in our study, the prevalence of physical and mental illnesses increased proportionally with increased age (data not shown). Moreover, with advanced age the proportion of widowed patients increases, which may result in loneliness and living alone, recognized risk factors for death in general population and in suicide attempters [6, 11, 20]. Indeed, the association of widowed condition with the risk of all-cause and unnatural-cause deaths was also observed in our study (data not shown).

Suicide attempters living in highly deprived areas were at 71% greater risk of mortality as compared to those living in less deprived areas, congruently with what observed elsewhere using income and education level as indicators of socioeconomic status [14, 32]. Patients of high deprived areas may be at higher risk of psychiatric disorders or physical illnesses, have limited access to social and medical resources, poor social support, bad diet habits, substance use related problems and poor skills to cope with adverse life situations compared to those of more advantaged areas. These characteristics may therefore exacerbate the negative outcomes of a frail condition as suicide attempt. Particular attention should be paid to patients of low socioeconomic level after suicide attempt.

The importance and mechanisms of family composition that may impact the effect of attempted suicide on mortality have been understudied. In our study, living in single-parent family was associated with an increased risk of all-cause and natural-cause mortality compared to living in couples with children. This is expected since, single parents may experience stressful life events, economic disadvantage, and social and psychological pressure to a greater extent than two-parent families. However, in a previous Finnish study, an increased risk of natural- and violent-cause mortality was observed among single-parent families of general population, but not among suicide attempters [11].

Accounting for all other variables included in the model, being affected by mood disorders was an independent risk factor for all-cause mortality, similarly to what observed in other studies [3, 7, 9, 13, 21, 33, 37]. However, although the direction of effect was consistent, the statistical significance was not reached when the impact on natural and unnatural deaths was tested separately, probably due to limited statistical power of the restricted sample. Moreover, due to violation of proportional hazard assumption, the results of the model assessing unnatural causes of death should be taken with caution. Nevertheless, these findings point out the need to apply particular attention in diagnosis of concurrent psychiatric disorders, and in prescribing effective treatment in order to prevent mortality risk.

As regards physical comorbidities, an increased risk of all-cause and natural-cause deaths was observed for patients suffering from malignant neoplasms and diabetes mellitus. Physical illnesses are significant predictors of death among suicide attempters [2, 5], especially in case of chronic and severe conditions. Moreover, it is recognised that suicidal patients with chronic conditions are more depressed [35], which may be associated with severe health outcomes. Finally, intracranial injury or skull fracture was also a significant predictor of all-cause mortality, a diagnosis that may be related to suicide attempt method itself, e.g. violent attempts could lead to serious traumatic injuries, and in these cases the risk of death can be higher.

This study has a number of strengths. The sample included all episodes of suicide attempts referred from hospitals and ED in the region, irrespective of the method used. Several information on the study subjects were collected from administrative and health registers ensuring richness of the data and investigation of both sociodemographic factors and comorbidities. Completeness of the mortality data was high. However, the study results should be considered also in a light of some limitations. The suicide attempts are potentially underestimated due to misclassified and underreported cases, i.e. those not accessing ED or hospital, and those registered with other diagnoses, e.g. accidents. So, the sample may not be fully representative of all suicide attempts in the regional catchment area but biased toward the most seriously affected cases. We did not have the information on cause-specific mortality for the whole timeline of the cohort, but only until 2018. Therefore, Cox regression models assessing natural and unnatural causes of death were run on restricted samples, possibly resulting in a loss of statistical power for some factors. Moreover, the comparison of results across studies may be challenging due to the ambiguous and inconsistent definition of suicide attempt sometimes including self-injurious acts with and without suicidal intent. Finally, the study would deserve a longer follow-up.

In conclusion, our results showed a risk of mortality particularly high within the first year after admission to hospital or ED for attempted suicide. Male gender, increased age, high area deprivation index, single-parent family, mood disorders, malignant neoplasm, diabetes mellitus and intracranial injury or skull fracture were important risk factors for mortality after suicide attempt. Focusing on these predictors can help to identify high-risk groups, inform clinicians on medical and psychiatric needs of suicidal patients, and plan outpatient care following hospital discharge. Our findings urge the need to design strategies for the assistance and care of these patients at long term in order to reduce the unfavourable outcomes.