Infection Control & Hospital Epidemiology Table 1. Demographics and Other Characteristics of the Medicare Elderly Population CDI Cases Total Characteristic
Age, mean y (SD) Female Race
White Black
Other race Prior LTCF residence
Dual eligibility for Medicare and Medicaid Acute-care hospitalization in the previous year SNF encounter in previous year
Note. LTCF, long-term care facility; SNF, skilled-nursing facility.
socioeconomic status. Residence in an LTCF prior to the index date was identified in 95,775 (6.4%), and 404,227 (27.1%) had been hospitalized at least once in the prior year. A total of 169,073 patients (11.3%) died within 1 year of the
CDI (control) index date. The all-cause mortality rates were 40.9% among CDI patients and 7.4% for control patients. Of the persons eligible for new LTCF and SNF, 23,700 of 1,381,830 (1.72%) became residents in an LTCF (7.39% of CDI and 1.17% of control patients) and 119,780 of 1,429,750 (8.38%) entered an SNF (37.52% of CDI and 5.48% of control patients) within 1 year. Of the patients who newly entered an LTCF, 5,598 (23.6%) were also resident in an SNF before transitioning to the LTCF. Of patients newly resident in an LTCF, 23% died within 1 year of the CDI (control) onset date; of patients newly resident in an SNF, 33.4% died within 1 year. The population eligible for subsequent hospitalization(s) included individuals whose CDI or control index dates occurred as outpatients, or for those hospitalized at their index date, those patients who were alive at hospital dis- charge (n=1,474,999). At least 1 hospitalization within 30, 90, and 365 days after the index date occurred in 76,691 patients (23.21% of CDI and 3.03% of control patients) within 30 days after the index date, in 162,022 patients (39.91% of CDI and 7.50% of control patients) within 90 days, and in 369,931 patients (58.93% of CDI and 21.00% of control patients) within 1 year. CDI was associated with a 1.77-fold increased risk of 30-day
all-cause mortality (95% confidence interval [CI], 1.74–1.81) in the propensity-score matched pairs analysis, and attributable mortality risk of 10.9% (Table 2 and Appendix Table 3). In sec- ondary analyses, CDI was associated with a 1.74-fold increased risk of new LTCF transfer (95% CI, 1.67–1.82; attributable risk, 2.7%) and a 2.52-fold increased risk of new SNF entry (95% CI, 2.46–2.58; attributable risk, 15.8%) within 30 days (Table 2). Matching was successful in 128,406 of 174,903 of the CDI cases (73.4%). The standardized differences and distribution of pro- pensity scores are shown in Appendix Figures 1 and 2. Unmat- ched CDI cases were older and had higher frequencies of virtually all risk factors, consistent with the propensity score distribution for CDI cases (Appendix Table 2 and Figure 2). The results of the stratified analysis for all-cause mortality are shown in Figure 1. The risk of mortality was highest in patients
Table 2. Outcomes Attributable to CDI in Propensity Score-Matched Pairs Analyses in the Elderly Medicare Population
Outcome Mortality within 1 y OR (95% CI)a 1.77 (1.74–1.81)
New transfer to LTCF within 1 y 1.74 (1.67–1.82) New transfer to SNF within 1 y 2.52 (2.46–2.58)
Acute-care hospitalization Within 30 d Within 90 d Within 1 y
2.27 (2.22–2.32) 1.95 (1.92–1.98) 1.52 (1.51–1.54)
term care facility; SNF, skilled nursing facility. aHazard ratios presented for acute-care hospitalizations.
with the lowest likelihood of CDI (ventile 1: HR, 3.04; 95% CI, 2.83–3.26), and this risk progressively decreased as the probability of CDI increased. In the highest-risk stratum, the risk of mortality was much lower but was still statistically significant (ventile 20: HR, 1.09; 95% CI, 1.01–1.17). As can also be seen in Figure 1, the percentage of CDI and control patients who died within 1 year progressively increased with increasing probability of CDI, from 8.8% of CDI cases and 3.0% of control patients in ventile 1, to 64.2% of CDI cases and 59.7% of control patients in ventile 20 with the highest probability of CDI. The same pattern was identified for new LTCF (Fig. 1) and
SNF transfers (Appendix Fig. 3). The highest risk of both out- comes occurred in the first stratum with lowest likelihood of CDI (LTCF: HR, 3.86; 95% CI, 3.20–4.65 and SNF: HR, 4.51; 95% CI, 4.17–4.89). The risk of both outcomes decreased with increasing likelihood of CDI, albeit not as dramatically as mortality. We analyzed 121,830 matched pairs for risk of acute-care hospitalizations. CDI was associated with increased risk of hos- pitalization within 30 days (HR, 2.27; CI, 2.22–2.32), within 90 days (HR, 1.95; CI, 1.92–1.98), and within 1 year (HR, 1.52; CI, 1.51–1.54), with attributable risk ranging from 11.4% to 15.7% (Table 2, Appendix Table 4). Similar results were obtained in the
Risk Difference, % 10.9 2.7
15.8
11.4 15.7 12.4
Note. CDI, Clostridium difficile infection; OR, odds ratio; CI confidence interval; LTCF, long-
(N=1,493,441), No. (%) 77.5 (7.9)
925,316 (62.0)
1,301,397 (87.1) 110,870 (7.4) 81,174 (5.4) 95,775 (6.4)
271,128 (18.2) 404,227 (27.1) 183,539 (12.3)
(N=174,903), No. (%)
80.5 (8.0) 112,251 (64.2)
153,857 (88.0) 13,801 (7.9) 7,245 (4.1)
40,143 (23.0) 56,376 (32.2) 148,066 (84.7) 93,595 (53.5)
Controls
(N=1,318,538), No. (%)
77.1 (7.7) 813,065 (61.7)
1,147,540 (87.0) 97,069 (7.4) 73,929 (5.6) 55,632 (4.2)
214,752 (16.3) 256,161 (19.4) 89,944 (6.8)
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