Table 3.
Comparison of primary care services areas (PCSAs) by degree of modularity
| PCSA characteristic | Modularity* ≥ 0.4 (N=151) | Modularity* < 0.4 (N=137) | p value | ||
|---|---|---|---|---|---|
| Mean ± SD | Median (IQR) | Mean ± SD | Median (IQR) | ||
| Population 65 or older, % | 12.5 ± 4.5 | 11.8 (9.3–14.7) | 15.9 ± 5.1 | 15.3 (12.1–19.7) | <.0001 |
| Non-Hispanic White, % | 36.2 ± 16.0 | 38.8 (26.9–47.1) | 40.5 ± 16.9 | 44.1 (30.8–54.2) | 0.0262 |
| Medicare Advantage member, % | 32.8 ± 11.1 | 31.1 (24.2–39.5) | 25.3 ± 10.1 | 23.1 (17.9–30.7) | <.0001 |
| Area Deprivation Index (ADI) (percentile)¥ | 60.1 ± 19.2 | 64 (45–74.5) | 69.7 ± 16.4 | 73 (58.5–81) | <.0001 |
| N (%) | |||||
| Population | <.0001 | ||||
| Q1: <14003 | 10 (6.6) | 62 (45.3) | |||
| Q2: 14003–38338 | 26 (17.2) | 46 (33.6) | |||
| Q3: 38339–115728 | 48 (31.8) | 24 (17.5) | |||
| Q4: >115728 | 67 (44.4) | 5 (3.6) | |||
| Median household income (dollar)# | 0.0058 | ||||
| Q1: <40358 | 32 (21.2) | 40 (29.2) | |||
| Q2: 40358–45838 | 30 (19.9) | 42 (30.7) | |||
| Q3: 45839–57430 | 40 (26.5) | 32 (23.4) | |||
| Q4: >57430 | 49 (32.5) | 23 (16.8) | |||
| Median household income (dollar), weighted‡ | 0.0030 | ||||
| Q1: <40893 | 33 (21.9) | 39 (28.5) | |||
| Q2: 40893–47815 | 29 (19.2) | 43 (31.4) | |||
| Q3: 47816–57399 | 39 (25.8) | 33 (24.1) | |||
| Q4: >57399 | 50 (33.1) | 22 (16.1) | |||
| Primary care provider availability§ | 0.0261 | ||||
| Q1: <14.1 | 28 (18.5) | 44 (32.1) | |||
| Q2: 14.1–25.2 | 46 (30.5) | 26 (19.0) | |||
| Q3: 25.3–37.9 | 40 (26.5) | 33 (24.1) | |||
| Q4: >37.9 | 37 (24.5) | 34 (24.8) | |||
| Number of provider dyads sharing ≥ 30 patients | <.0001 | ||||
| Q1: <2 | 13 (8.6) | 61 (44.5) | |||
| Q2: 3–9 | 24 (15.9) | 46 (33.6) | |||
| Q3: 10–25 | 50 (33.1) | 22 (16.1) | |||
| Q4: >25 | 64 (42.4) | 8 (5.8) | |||
PCSAs consisted of Census blocks. This variable is the median of the census-block level of the national ADI percentile.
PCSAs consisted of Census tracts. This variable is the median of the census-tract level of household income.
This variable is the median of the census-tract level household income, weighted by the number of households in the census tract.
Calculated as the number of primary care providers who had any Medicare Part B bills in 2015 per thousand Medicare beneficiaries in the PCSA.
The modularity was estimated from SNA where the number of shared patients was used as the weight of the edge, i.e., the tie between two providers. Modularity is a measure of community clustering, with a high modularity indicating the density of connections within communities. A network is modular insofar as the modules within it are densely connected, while connections between modules are sparser. A previous study suggested a modularity larger than 0.3–0.4 is a clear indication that the subgraphs of the corresponding partition are modules [12]. Therefore, we used the cutoff of 0.4 to identify the communities that are in the well-defined modules within the PCSA.
SD: standard deviation; IQR: interquartile range.