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. Author manuscript; available in PMC: 2017 Feb 1.
Published in final edited form as: Semin Arthritis Rheum. 2015 Jul 28;45(4):511–518. doi: 10.1016/j.semarthrit.2015.07.007

Table 3.

Unadjusted and adjusted proportions of Medicare beneficiaries travelling ≥ 90 minutes to visit a rheumatologist (row percents).

Characteristics Unadjusted proportion (95% CI)
Adjusted Proportion (95% CI)¥
Model 1 Model 2§ Model 3§
Individual-level factors Age
 18–64 (ref) 0.09 (0.08, 0.09) 0.08 (0.07, 0.09) 0.09 (0.08, 0.11) 0.09 (0.08, 0.10)
 65–74 0.08 (0.08, 0.08) 0.07 (0.06, 0.07)* 0.08 (0.07, 0.09)* 0.08 (0.07, 0.09)*
 ≥75 0.06 (0.06, 0.06)* 0.05 (0.04, 0.05)* 0.07 (0.06, 0.08)* 0.07 (0.06, 0.07)*
Sex
 Male (ref) 0.08 (0.08, 0.09) 0.07 (0.06, 0.08) 0.08 (0.07, 0.10) 0.08 (0.07, 0.09)
 Female 0.07 (0.07, 0.07)* 0.06 (0.05, 0.06)* 0.08 (0.07, 0.09)* 0.07 (0.06, 0.08)*
Race/ethnicity
 White (ref) 0.08 (0.07, 0.08) 0.08 (0.08, 0.09) 0.09 (0.08, 0.10) 0.09 (0.08, 0.10)
 Non-white 0.05 (0.04, 0.05)* 0.05 (0.04, 0.05)* 0.07 (0.06, 0.08)* 0.07 (0.06, 0.08)*
State Buy-In
 No (ref) 0.07 (0.07, 0.07) 0.06 (0.06, 0.07) 0.09 (0.08, 0.10) 0.08 (0.07, 0.09)
 Yes 0.07 (0.06, 0.07) 0.06 (0.06, 0.07) 0.07 (0.06, 0.09)* 0.07 (0.06, 0.08)*
Area-level factors ZIP-based SES indicatora
 Tertile 1 (low; ref) 0.11 (0.11, 0.12) 0.09 (0.08, 0.10) 0.09 (0.08, 0.10)
 Tertile 2 0.07 (0.06.0.07)* 0.08 (0.07, 0.09)* 0.07 (0.06, 0.08)*
 Tertile 3 (high) 0.04 (0.03, 0.04)* 0.07 (0.06, 0.09)* 0.07 (0.06, 0.08)*
Supply of rheumatologists in beneficiary HSAb
 None (ref) 0.12 (0.12, 0.14) 0.13 (0.12, 0.15) 0.13 (0.11, 0.14)
 > 0 – < 0.65 0.02 (0.02, 0.02)* 0.05 (0.05, 0.06)* 0.05 (0.04, 0.06)*
 ≥0.65 0.03 (0.03, 0.03)* 0.07 (0.06, 0.08)* 0.07 (0.06, 0.08)*
Rural-Urban Area category of beneficiary ZIP codec
 Rural (ref) 0.27 (0.24, 0.30) 0.18 (0.16, 0.21) 0.17 (0.15, 0.19)
 Small Town 0.19 (0.17, 0.21)* 0.11 (0.10, 0.13)* 0.11 (0.09, 0.12)*
 Micropolitian area 0.13 (0.12, 0.14)* 0.08 (0.07, 0.10)* 0.08 (0.07, 0.09)*
 Metropolitan area 0.02 (0.02, 0.02)* 0.02 (0.02, 0.02)* 0.02 (0.02, 0.02)*
Medicare reimbursement rate of beneficiary HSAd
 Quartile 1 (low; ref) 0.08 (0.07, 0.08) 0.10 (0.09, 0.12)
 Quartile 2 0.04 (0.04, 0.05)* 0.07 (0.06, 0.08)*
 Quartile 3 0.04 (0.03, 0.04)* 0.07 (0.06, 0.08)*
 Quartile 4 (high) 0.04 (0.04, 0.04)* 0.06 (0.05, 0.07)*
C statistic 0.57 0.75 0.75
¥

Values represent the adjusted proportion of patients travelling ≥ 90 minutes at each variable level (row percents). In each column, proportions were adjusted for the variables listed; additionally, Models 2 and 3 adjust for clustering of patients within provider ZIP code. Starred values are significantly different from the other variable levels.

a

Agency for Healthcare Research and Quality’s socioeconomic (SES) indicator variables based on ZIP code.

b

Number of Medicare Fee-for-service rheumatologists per 100,000 residents per Hospital Service Area.

c

Health Resources and Services Administration’s Rural-Urban Commuting Area (RUCA) codes.

d

Dartmouth Atlas of Health Care’s Medicare Reimbursement rate.