Fig. 1

Study Population, Sampling, and Cohort Assembly. Medicare Beneficiaries = enrolled under Medicare and living thorough 2016; Part B = traditional Medicare fee-for-service outpatient coverage; Part D = Medicare pharmacy coverage; Opioid = subject with opioid prescription fill; Recipients = subject who received chiropractic care; Early = recipient of chiropractic care within 30 days following index date; Delayed = recipient of chiropractic care within 31–90 following index date; Late = recipient of chiropractic care within 91–120 following index date; Inclusion Criteria = Medicare beneficiaries alive as of 12/31/16, living in a US state or the District of Columbia, aged 65–99 years, continuously enrolled throughout the study period in Medicare Parts B, with Part D coverage at index date plus 365 days, with at least 2 office visits between 7 and 90 days apart to a primary care physician and/or Doctor of Chiropractic, claimed under Medicare Part B with date of service 2012–2016 and payment amount greater than zero for a primary diagnosis of spine-related disorder. Exclusion Criteria = beneficiaries enrolled in Medicare Part C, with primary diagnosis of cancer or receiving hospice care during 2012–2016, or opioid prescription fill that occurred before the index date