Table 2.

Adjusted mortality hazards ratios associated with provider visit frequency

Visit FrequencyCox Proportional Hazards ModelaTime-Variable Cox Proportional Hazards ModelbInstrumental Variable Analysisc
AHR (95% CI)PAHR (95% CI)PProbability Difference (%)dP
<4 visits/mo11
4 visits/mo0.98 (0.96–1.01)0.160.98 (0.96–1.00)0.050.070.88
  • AHR, adjusted hazard ratio; CI, confidence interval.

  • a Adjusted for age, sex, race, ethnicity, primary cause of ESRD, year of dialysis initiation, comorbidity score, socioeconomic status, dual eligibility status, urban status, number of dialysis sessions during run-in, hospitalization days during run-in, body mass index, estimated GFR, hemoglobin, and albumin at dialysis initiation (1 year follow-up).

  • b Exposure variable updated every 3 months. Adjusted for age, sex, race, ethnicity, primary cause of ESRD, year of dialysis initiation, comorbidity score, socioeconomic status, urban status, number of dialysis sessions during run-in, hospitalization days during run-in, body mass index, estimated GFR, hemoglobin, and albumin at dialysis initiation. Comorbidity score, number of dialysis sessions (compliance), and number of hospitalization days were updated every 3 months. Follow-up until December 31, 2009.

  • c Bivariate probit models for different outcomes adjusted for age, sex, race, ethnicity, primary cause of ESRD, year of dialysis initiation, comorbidity score, socioeconomic status, dual eligibility status, urban status, number of dialysis sessions during run-in, hospitalization days during run-in, body mass index, estimated GFR, hemoglobin, and albumin at dialysis initiation.

  • d Probability difference of corresponding event when there are at least four visits in the run-in period compared with less than four visits given other covariates evaluated at the mean values.