Sex Differences in Hospitalizations with Maintenance Hemodialysis

Abstract

Hospitalization is a major source of morbidity among patients with ESRD undergoing maintenance hemodialysis and is a significant contributor to health care costs. To identify subgroups at the highest risk of hospitalization, we analyzed by sex, age, and race, adjusting for demographic and clinical characteristics, the hospitalization rates, and 30-day readmissions for 333,756 hospitalizations among 111,653 patients undergoing maintenance hemodialysis in facilities operated by a large dialysis organization in the United States (2007-2011). The overall hospitalization rate was 1.85 hospitalizations per person-year and was much higher among women than among men (2.08 versus 1.68 hospitalizations per year for women versus men, P<0.001). Age group-specific hospitalization rates were consistently higher for women than for men of the same race, and the differences were greatest in younger age groups (for example, women aged 18-34 years and ≥75 years had 54% [95% confidence interval, 42% to 67%] and 14% [95% confidence interval, 11% to 18%] higher hospitalization rates, respectively, than did men of respective ages). Women also had substantially higher risk for 30-day readmission, with the largest differences at younger ages. Women had a significantly lower serum albumin level than men, and stratification by serum albumin level attenuated sex differences in the age group-specific hospitalization and 30-day readmission rates. These findings suggest that women undergoing maintenance hemodialysis have substantially higher risks for hospitalization and 30-day readmission than men. In this cohort, the sex differences were greatest in the younger age groups and were attenuated by accounting for differences in health status reflected by serum albumin level.

Keywords: end stage kidney disease; hemodialysis; hospitalization.

Figure 1.

Sex differences in hospitalization and 30-day readmissions vary by age in patients undergoing thrice-weekly hemodialysis. Adjusted incidence rate ratios (IRRs) of hospitalization (left) and difference in adjusted probability of readmission within 30 days of discharge (right), comparing women to men by age. Error bars represent 95% CIs. Hospitalization IRRs and readmission probability adjusted for race, geographic region, calendar year of dialysis initiation, time since initiation of dialysis, insurance, Charlson comorbidity index, diabetes, and cardiovascular comorbidities, and the interaction of age and race.

Figure 2.

The sex differences in hospitalization and 30-day readmission are attenuated and do not vary by age when stratified by serum albumin. Adjusted incidence rate ratio (IRR) of hospitalization (left) and difference in adjusted probability of readmission within 30 days of discharge (right) comparing women to men by age, stratified by serum albumin. Error bars represent 95% CIs. Hospitalization IRRs and readmission probability adjusted for race, geographic region, calendar year of dialysis initiation, time since initiation of dialysis, insurance, Charlson index, diabetes, and cardiovascular comorbidities, and the interaction of age and race. Pr(30d readmit), Probability of readmission within 30 days of discharge.

Figure 3.

Sex differences in hospitalization persist and vary by age when stratified by the type of vascular access. Adjusted incidence rate ratio (IRR) of hospitalization comparing women to men by age, stratified by vascular access (CVC, central venous catheter; AV, arteriovenous access). There was no difference in the IRR, comparing women to men by age, in individuals with different vascular access types.

Figure 4.

Adjusted IRR of hospitalization comparing women to men by age, stratified by quartiles of clinical variables. To facilitate comparison, stratification by albumin (as in Figure 2) and vascular access (Figure 3) are included. Laboratory variables were categorized into quartiles except albumin (<3.50, 3.50–3.79, 3.80–3.99, ≥4 mg/dl), body mass index (<18, 18–24.9, 25–29.9, 30–39.9, ≥40 kg/m²), hemoglobin (<9, 9–9.9, 10–10.9, ≥11 g/dl), calcium (<8.5, 8.5–8.9, 9.0–9.4, 9.5–10.1, ≥10.2 mg/dl), and phosphorous (<4.5, 4.6–5.3, 5.4–6.3, ≥6.4 mg/dl). Vascular access was central venous catheter (squares) or any arteriovenous method (circles).