Background: Poisoning injuries is an increasing concern among older people, and so is the repetition of intentional poisonings. To date, few studies have documented the pattern and individual risk factors for repeated poisonings. This national study aims to shed light on the burden, pattern, and health-related risk factors of repeated intentional poisoning leading to hospitalization or death among older Swedish adults (50 years and older), with a focus on the year following a first event.

Methods: We conducted a nationwide register-based cohort study of people aged 50-100, hospitalized for intentional poisoning (ICD10: X60-69) during 2006-2016 (n = 15,219) and re-hospitalized by poisoning of any intent within a year (n = 1710), i.e., up to the end of 2017. We considered in turn, the distribution of the second poisoning in 30-day intervals stratified by intent; poisoning lethality within a month and a year; and the sex-specific association between health conditions and being re-hospitalized for intentional poisoning within one year as compared to being hospitalized only once using logistic regression (odds ratios (OR) with 95% confidence intervals (95% CI)).

Results: Following an intentional poisoning, re-hospitalization within a year was predominantly for a new intentional poisoning (89.7%) and occurred most typically within a month (median 4 days). Death within 30 days occurred in similar proportion for the first and second poisoning (2.3% vs. 2.1% respectively). Among both men and women, comorbidity of psychiatric illness was strongly associated with re-hospitalization for intentional poisoning (adjusted ORs = 1.70; 95% CI = 1.45-2.01 and 1.89 (95% CI = 1.60-2.19) respectively).

Conclusion: Most re-hospitalizations within a year after intentional poisoning are also for intentional poisoning and occur most typically within days. Re-hospitalization is associated with several conditions that are characteristic of poor mental health and there are more similarities than differences between men and women in that respect.