INTRODUCTION Substance misuse (SM) remains a challenging public health concern despite substantial evidence from traditional research methods for effective interventions. Studies which used whole population linked data are scarce but may be useful in informing early identification and prevention of escalation. We examined the type and timing of healthcare service contacts in those presenting with SM-related issues in Wales to describe sociodemographic characteristics and quantify the frequency of pre-and-post index SM healthcare contacts as potential opportunities for preventative interventions. We defined the index as the first SM-related record in healthcare settings.

METHODS We conducted a whole population cohort study on 168 774 persons aged at least 10 years whose index SM contact with health services was between 1 January 2010 and 31 December 2019. We examined their records both prospectively and retrospectively for 2 years from the index SM event date.

RESULTS Inpatient admission (36.0%) and primary care (30.0%) were the main points of first SM-related contact. Median age was 39 years; the majority were males (62.3%) of white ethnicity (71.0%). One in four lived in the most deprived areas. The majority (60.3%) had alcohol as the problem substance at baseline. Approximately 38.0% (63 520) of the cohort had at least a second SM-related event within 24 months postindex SM event, indicating potential missed opportunities for referral to relevant SM specialist treatment services. Inpatient admissions increased by 71.0% after the index SM date (ISMD) compared with pre-ISMD (84 237 and 49 327, respectively). Injury, poisoning and digestive disorders were the most frequent reasons for admissions. However, admissions relating to mental disorders more than tripled after the ISMD (8421 admissions from 2696 patients-a 212.0% increase). Similar increases were found in emergency and GP contacts. Around 1.0% had their first SM record captured at death.

CONCLUSION Individuals with SM records are frequent attendees to healthcare services, particularly after their index SM event. Healthcare contacts represent vital opportunities to engage those with SM issues early to reduce harm and potential escalation of use and refer to specialist treatment and support.