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. Author manuscript; available in PMC: 2013 Sep 1.
Published in final edited form as: Spine (Phila Pa 1976). 2012 Sep 1;37(19):1693–1701. doi: 10.1097/BRS.0b013e3182541f45

Table 2.

Linear Regression Models to Predict Annual Expenditures (2008$)a on Ambulatory Visits to US Medical Physicians, Chiropractors, and Physical Therapists for Spine Conditions

Medical Care Chiropractic Care Physical Therapy
Coefficient (95% CI) P-
value
Coefficient (95% CI) P-
value
Coefficient (95% CI) 1,358 P-
value
No. of MEPS Respondents in Sample 7,647 4,507 1,358
Yearb 1.04 (1.02, 1.05) <0.001 1.02 (1.00, 1.04) 0.06 0.99 (0.96, 1.01) 0.31
Age 1.00 (1.00, 1.00) 0.45 1.00 (1.00, 1.00) 0.72 1.01 (1.00, 1.01) 0.00
Gender
 male 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 female 0.99 (0.92, 1.06) 0.70 1.16 (1.07, 1.27) 0.00 1.22 (1.05, 1.41) 0.01
US Region
 Northeast 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 Midwest 0.90 (0.80, 1.02) 0.09 0.89 (0.78, 1.03) 0.11 0.94 (0.75, 1.18) 0.61
 South 0.87 (0.78, 0.97) 0.01 1.02, 0.89, 1.17) 0.81 0.93 (0.75, 1.15) 0.51
 West 0.91 (0.80, 1.03) 0.15 0.90 (0.79, 1.03) 0.13 0.82 (0.65, 1.02) 0.08
Rurality
 Non-MSA 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 MSA 1.03 (0.94, 1.13) 0.46 1.44 (1.28, 1.61) <0.001 1.03 (0.85, 1.24) 0.79
Race/Ethnicity
 Hispanic 1.01 (0.88, 1.16) 0.89 0.98 (0.78, 1.23) 0.87 0.73 (0.55, 0.98) 0.04
 Non-Hispanic White 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 Non-Hispanic Black or African American 0.96 (0.85, 1.08) 0.46 1.18 (0.94, 1.47) 0.15 1.02 (0.78, 1.34) 0.87
 Other or multiple races 0.89 (0.74, 1.08) 0.24 1.25 (0.99, 1.59) 0.06 1.23 (0.86, 1.75) 0.27
Marital status
 married 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 divorced, separated, or widowed 0.95 (0.87, 1.04) 0.30 1.03 (0.92, 1.16) 0.57 0.97 (0.81, 1.15) 0.71
 never married 0.94 (0.83, 1.07) 0.36 1.02 (0.89, 1.17) 0.78 1.07 (0.84, 1.35) 0.59
Employment status
 employed 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 ever unemployed (or retired) during year 1.03 (0.94, 1.13) 0.56 1.00 (0.90, 1.09) 0.92 0.92 (0.77, 1.11) 0.38
Education
 high school graduate or less 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 some college or associate's degree 1.05 (0.94, 1.18) 0.37 1.06 (0.94, 1.19) 0.33 0.88 (0.71, 1.10) 0.27
 bachelor’s or graduate degree 1.11 (1.01, 1.23) 0.04 1.04 (0.93, 1.17) 0.49 0.99 (0.82, 1.19) 0.91
Health Insurance Coverage
 private 1.36 (1.18, 1.57) <0.001 1.21 (1.03, 1.43) 0.20 1.02 (0.66,1.57) 0.95
 public 1.06 (0.90, 1.25) 0.46 0.97 (0.79, 1.18) 0.74 0.66 (0.41, 1.05) 0.08
 uninsured 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
Any Limitation
 No 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 Yes 1.52 (1.40, 1.65) <0.001 1.21 (1.10, 1.34) <0.001 1.23 (1.06, 1.42) 0.07
Self-reported Health Status
 Excellent, Very Good, or Good 1.00 (Reference) 1.00 (Reference) 1.00 (Reference)
 Fair or Poor 1.36 (1.23, 1.50) <0.001 1.06 (0.94, 1.20) 0.34 1.12 (0.92, 1.36) 0.25

Abbreviations: MEPS, Medical Expenditure Panel Survey; CI, Confidence Interval

a

Linear regression models predict annual expenditures in hundreds (2008$, log transformed)

b

Test of trend (Year included in models as a categorical variable)