Table 2. Bivariate Probit Equations for the Probability of Regular Primary Care and the Probability of Blood Pressure Control (Year and quarter fixed effects are not shown).
VariableProbability of Regular Primary CareProbability of Blood Pressure Control
Coefficient (Δz)P Value95% CICoefficient (Δz)P Value95% CI
Demographics
    Age0.027.000***0.021–0.033−0.029.000***−0.034 to −0.023
    Female sex0.088.000***0.055–0.1200.047.001**0.019–0.075
Diabetes mellitus
    Duration0.062.359−0.070 to 0.1940.005.401−0.017 to 0.007
    Duration × age0.019.524−0.040 to 0.0780.000.1850.000–0.000
    Diagnosed−0.007.322−0.022 to 0.0070.217.001**0.093–0.341
    Identified from registry0.000.003**−0.001 to 0.0000.102.000***0.051–0.153
    Duration × registry0.029.000***0.020–0.037−0.014.000***−0.021 to −0.006
Risk factors
    Insulin prescribed0.213.000***0.177–0.2490.045.005**0.013–0.076
    High LDL diagnosed0.275.000***0.226–0.324−0.193.000***−0.239 to −0.147
    BMI−0.087.000***−0.116 to −0.057−0.047.000***−0.068 to −0.026
    Excess BMI0.121.000***0.091–0.150−0.005.657−0.016 to 0.026
    BMI × age0.000.000***−0.001 to 0.0000.001.000***0.000–0.001
    Hypertension index−0.239.000***−0.255 to −0.223
    Blood pressure index−0.025.000***−0.033 to −0.018
    Tobacco smoker−0.152.000***−0.186 to −0.1190.049.001**0.019–0.078
    Smokeless tobacco user0.198.000***0.146–0.250−0.013.556−0.029 to 0.054
Access
    Matanuska-Susitna borough resident−0.653.000***−0.706 to −0.601
    Outside service area−0.078.010*−0.137 to −0.019
    Miles to primary care−0.010.000***−0.012 to −0.0070.000.000***0.000–0.000
Primary care
    Nutrition/exercise classes (instrument)0.022.001**0.009–0.035
    Regular primary care0.702.000***0.473–0.930
    Constant2.238.000***1.458–3.0181.421.000***0.809–2.034
Summary statistics
    ρ−0.306.000***
    Log likelihood−39,783
    Wald χ2 (70)4,656.000***
    Observations39,504
  • * P < .05;

  • ** P < .01;

  • *** P < .001

  • Hypertension index, derived from blood pressure measured during the initial encounter: 0 if systolic blood pressure (SBP) <120 and diastolic blood pressure (DBP) <80; 1 if 120 ≤ SBP < 140 or 80 ≤ DBP < 90; 2 if 140 ≤ SBP < 160 or 90 ≤ DBP <100; 3 if SBP ≥160 or DBP ≥100.

  • Blood pressure index, derived from blood pressure measured during the initial encounter: (SBP − 100)/20 + (DBP − 70)/10.

  • BMI, body mass index; CI, confidence interval; LDL, low-density lipoprotein.