OBJECTIVES: Health insurance plans increasingly are restricting their provider networks in efforts to lower spending. While there are potential benefits to provider selection, access to care could worsen if networks are too constrained to meet patient needs. We examined changes in provider networks over time and associations with primary care visit rates.

METHODS: Using data from the Massachusetts All Payer Claims Database (APCD) between 2009-2013, we focused on adult enrollees in two individual insurance market plans experiencing large enrollment changes. We empirically defined provider networks based on providers with in-network visits for primary care with adult plan enrollees. We defined the PCP network density within Hospital Referral Regions (HRRs) as the number of PCPs per 1,000 insured patients in the HRR. Using linear regression with patient-level fixed effects, we examined the association between PCP network density and PCP visit rates, while adjusting for time-changing demographics, enrollment, and what fraction of each PCP’s panel consisted of plan enrollees.

RESULTS: PCP network density per HRR decreased between 2010-2013 in Plan 1 by an average of 38% (from 106 to 65 PCPs/1,000 enrollees), but density increased in Plan 2 by 107% over the same period. After multivariate adjustment, the mean PCP visit rates dropped by 0.46 visits per year (95%CI: 0.42-0.51) for each decrease of 100 PCPs/1,000 enrollees per HRR. The density change and visit reduction association was larger among existing plan members than among new enrollees, e.g., a decrease of 0.60 visits per year (95%CI: 0.55-0.65) and of 0.32 visits per year (95%CI: 0.27-0.37), respectively, for each decrease of 100 PCPs/1,000 enrollees.

CONCLUSIONS: The provider network sizes for adult primary care per plan enrollee in the local area changed substantially. When the PCP network plan density dropped, so did visit rates.