OBJECTIVES: This study compared the economic outcomes and absenteeism of chiropractic users to non-users.

METHODS: This study used a retrospective matched case-control design, utilizing year 2015 nationally representative Medical Expenditure Panel Survey (MEPS) database. Chiropractic utilization was defined as six or greater visits to a chiropractor in the first half of the year, among adults age 18 and older. Visitors to a chiropractor, not meeting the visit criteria were excluded. A propensity score (PS) model was developed, using backwards stepwise logistic regression, predicting chiropractic utilization. The scores were applied using a greedy one-treated to two-control matching technique, caliper set at 0.5. Outcomes considered include days missed from work/school, mean out-of-pocket medical expenses, and mean total medical expenses. Data analyses were completed using SAS version 9.4, significance set at 0.05.

RESULTS: There were 229,905,173 (94.02%) adults classified as non-chiropractic users, 3,255,865 (1.33%) chiropractic users that met inclusion criteria, and 11,354,126 (4.64%) visitors to a chiropractor that did not meet the visit inclusion criteria. Before PS matching, the treatment and control groups differed significantly (p-value <0.05) on: age, presence of neck/back pain or injury, BMI, region of residence, insurance coverage, education, and comorbidities. There were 261 treated observations matched with 521 controls (weighted frequencies of 3,255,865 and 5,717,947, respectively). After matching, groups differed significantly only on BMI (28.03 treated versus 27.40 control) and age (52.48 treated versus 52.97 control). The treated group had significantly fewer days of missed work/school (8.51 versus 10.01). The treated group had significantly higher mean out-of-pocket medical expenses ($2,270 versus $973) and mean total medical expense ($11,857 versus $9,623).

CONCLUSIONS: Those treated by a chiropractor had significantly higher out of pocket and total medical expenses, a result that differs from prior published literature. However, those treated missed less work/school. The cost-effectiveness of chiropractic services for this sub-population should be examined more closely.