Effects of chiropractic use on medical healthcare utilization and costs in adults with back pain in Ontario, Canada from 2003 to 2018: a population-based cohort study.

BACKGROUND: Adults with back pain commonly consult chiropractors, but the impact of chiropractic use on medical utilization and costs within the Canadian health system is unclear. We assessed the association between chiropractic utilization and subsequent medical healthcare utilization and costs in a population-based cohort of Ontario adults with back pain. METHODS: We conducted a population-based cohort study that included Ontario adult respondents of the Canadian Community Health Survey (CCHS) with back pain from 2003 to 2010 (n = 29,475), followed up to 2018. The CCHS data were individually-linked to individual-level health administrative data up to 2018. Chiropractic utilization was self-reported consultation with a chiropractor in the past 12 months. We propensity score-matched adults with and without chiropractic utilization, accounting for confounders. We evaluated back pain-specific and all-cause medical utilization and costs at 1- and 5-year follow-up using negative binomial and linear (log-transformed) regression, respectively. We assessed whether sex and prior specialist consultation in the past 12 months were effect modifiers of the association. RESULTS: There were 6972 matched pairs of CCHS respondents with and without chiropractic utilization. Women with chiropractic utilization had 0.8 times lower rate of cause-specific medical visits at follow-up than those without chiropractic utilization (RR5years = 0.82, 95% CI 0.68-1.00); this association was not found in men (RR5years = 0.96, 95% CI 0.73-1.24). There were no associations between chiropractic utilization and all-cause physician visits, all-cause emergency department visits, all-cause hospitalizations, or costs. Effect modification of the association between chiropractic utilization and cause-specific utilization by prior specialist consultation was found at 1-year but not 5-year follow-up; cause-specific utilization at 1 year was lower in adults without prior specialist consultation only (RR1year = 0.74, 95% CI 0.57-0.97). CONCLUSIONS: Among adults with back pain, chiropractic use is associated with lower rates of back pain-specific utilization in women but not men over a 5-year follow-up period. Findings have implications for guiding allied healthcare delivery in the Ontario health system.