Background Opioid analgesics may increase the risk of falls, particularly among older adults. Few studies include individuals of all ages, and there is a need for robust measures of real-world opioid use and to account for additional risk factors including frailty and prior falls.

Objective To quantify age-related risk of serious fall events among adults prescribed opioids, by opioid exposure, time from initiation, and opioid dose.

Methods This population-based cohort study of new opioid users involved linkage of pharmaceutical claims to national and state health service datasets including information on medicines use, health services utilisation, and mortality. Adult residents of New South Wales, Australia, initiating prescription opioid treatment (defined as no dispensings in the preceding 365-days) between 01/01/2005 and 31/12/2018 were included. Time-dependent periods of opioid exposure were evaluated from dispensing records. Falls were identified from emergency department, hospitalisation, and mortality records. Negative binomial models were used to assess associations between time-dependent opioid exposure (overall, by time from initiation, and by dose), age, and risk of falls, adjusting for known risk factors including other fall risk-increasing drugs, frailty, and prior fall events.

Results The cohort comprised 3,212,369 individuals initiating prescription opioids (53% female, median age 49-years at cohort entry). Overall, 506,573 fall events were identified, including 5,210 fatal falls. During periods of current opioid exposure, risk of fall events was elevated among all age groups; compared with the 18–44-year age group; risk was highest among those aged ≥85-years (adjusted incident rate ratio 6.35, 95% confidence interval 6.20 to 6.51). Across all age groups, the first 28-days following initiation was a time of increased fall risk, with risk increasing with age. Among individuals aged 18–84-years, associations were identified between higher daily opioid doses and fall events.

Conclusions Exposure to prescription opioids was associated with increased risk of serious fall events among adults of all ages, with older individuals at greatest risk. These risks should be considered when prescribing opioids, particularly for individuals with pre-existing risk factors or where opioids are prescribed at higher doses. Targeted falls prevention efforts may be most effective within the first month following opioid initiation.