Hyperglycemia and mortality in elderly patients with Staphylococcus aureus bacteremia.

Objective: To investigate the association between hyperglycemia and in-hospital mortality in elderly patients with Staphylococcus aureus bacteremia (SAB).

Methods: We reviewed the medical records of 135 elderly patients with SAB admitted to two tertiary medical centers from January 2003 until December 2004. Patients were stratified into two groups: those with a 7-day post-SAB mean blood glucose <170 mg/dL and those with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL. A stepwise logistic regression analysis was performed to determine whether the degree of hyperglycemia was a significant predictor of mortality.

Results: Seventy-four (54.8%) patients had methicillin-resistant Staphylococcus aureus bacteremia. During the follow-up period from admission until discharge, 36 (26.7%) patients died. Twenty-one (21.4%) of 98 patients with a 7-day post-SAB mean blood glucose <170 mg/dL died, while 15 (40.5%) of 37 patients with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL expired. Multivariate analysis identified 3 independent determinants of death: Simplified Acute Physiology Score (SAPS) score at onset of SAB >45 (OR 5.3, 95% CI{1.8, 15.5}, P = 0.002), a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL (OR 3.3, 95% CI{1.2, 9.2}, P = 0.03), and altered mental status at the onset of SAB (OR 7.8, 95% CI{2.5, 23.9}, P = 0.0003).

Conclusions: Hyperglycemia is an important marker of increased mortality among hospitalized elderly patients with SAB.

Key Words: Staphylococcus aureus, mortality, elderly, hyperglycemia

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Staphylococcus aureus is an increasingly common cause of bacteremia in elderly patients. (1) It is associated with a significant morbidity and mortality among this group of patients. (2) Acute hyperglycemia is frequently encountered in stress situations. (3) The definition of stress hyperglycemia varies but is often defined as a plasma glucose level above 200 mg/dL. (4) Critically ill patients become hyperglycemic for several reasons. Several adaptive mechanisms such as increased epinephrine, cortisol, and glucagon secretion result in insulin resistance. These counterregulatory hormones increase the gluconeogenesis and glycogenolysis and decrease the use of glucose by down-regulating glycolysis and glycogen synthesis. In addition, they exacerbate hyperglycemia in the setting of limited insulin secretory capacity. Furthermore, it is not uncommon for ill patients to become insulin deficient due to a variety of reasons such as old age, pancreatitis, or hypoxemia. (5) It is well recognized that a reduction in insulin activity is often present in critically ill elderly patients, as well as in elderly patients with impaired glucose tolerance and overt diabetes. The reduction of muscle mass and function in the elderly could potentially result in impaired glucose utilization and storage with worsening hyperglycemia. (6)

Several studies have shown that hyperglycemia, even in patients without diabetes, is associated with increased in-hospital mortality and morbidity. (7-10) Targeted glycemic control has been shown to improve mortality, morbidity, and healthcare economic outcomes in the hospital setting. (11) However, these previous studies involved a heterogeneous patient population in terms of age. Therefore, it may be inappropriate to suggest that hyperglycemia is a marker of increased mortality among the elderly patients. Furthermore, few studies have evaluated the impact of hyperglycemia in patients with infections. (12,13) The aim of this study was to determine whether the degree of hyperglycemia has an impact on in-hospital mortality in elderly patients with Staphylococcus aureus bacteremia (SAB).

Patients and Methods

A retrospective cohort study was conducted at two tertiary medical centers: the University of Oklahoma Health Sciences Center and Oklahoma City Veteran Affairs Medical Center. The human subjects committee and the institutional review board of both institutions approved the study. Every patient with SAB from January 2003 until December 2004 was identified by review of blood culture results from the microbiology laboratory in each hospital. Patients who were younger than 60 years of age were excluded from the study. All in-patients who were [greater than or equal to]60 years of age and had one or more positive blood cultures for Staphylococcus aureus were included in the study. Patients who had missing capillary or plasma glucose levels for more than one day were not included in the study. If the same patient developed SAB with the same strain more than once, the first episode was included in the study and further episodes were excluded from the data analysis. Patients were followed until discharge from the hospital or death once included in the study. All study variables were obtained via review of the inpatient medical record. Patient information was collected regarding demographic characteristics, concurrent medical conditions, Charlson Weighted Index of Comorbidity (WIC), the Simplified Acute Physiology Score (SAPS) at onset of SAB, blood culture results, onset of SAB, appropriate antibiotic therapy, and in-hospital mortality. The onset of SAB was determined by the date of the first blood culture that grew Staphylococcus aureus. SAB was considered nosocomial if it developed >48 hours after hospital admission.

Data on the extent of glycemic control before onset of SAB included glycated hemoglobin (HbA1c) within 2 months of onset of SAB. We also estimated blood glucose after onset of SAB as the mean capillary blood glucose in the 7 days after the onset of SAB. The mean capillary blood glucose levels in the 7 days after the onset of SAB were calculated by averaging the highest daily values obtained clinically by finger stick. If capillary blood values were not available for the given period, we estimated the capillary blood glucose as 90% of the serum glucose value. (14) Patients were stratified into two groups: those with a 7-day post-SAB mean blood glucose <170 mg/dL and those with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL. Hypoglycemia was defined as any blood glucose value less than 50 mg/dL in the presence of symptoms of hypoglycemia documented in the chart.

Appropriate antimicrobial therapy was defined as the use of adequate dose of an antibiotic to which the isolated Staphylococcus aureus was susceptible in vitro within 48 hours of the first positive blood culture. The primary endpoint of the study was in-hospital death from any cause after the onset of SAB.

Statistical Analysis

Descriptive statistics were used to summarize the data. Categorical variables were analyzed using [chi square] test or Fisher's exact test, whereas continuous variables were analyzed by Wilcoxon rank sum test. To determine the predictors of mortality of elderly patients with SAB and whether the degree of hyperglycemia had an impact on the overall hospital mortality, a stepwise logistic regression analysis was performed. The model was verified by forward and backward variable insertion. Multiple variables were considered as possible predictors of mortality. These variables were selected based on their clinical and statistical importance. In addition to a 7-day post-SAB mean blood glucose level, other prognostic variables included an SAPS score >45 on the day of SAB, nosocomial SAB, the type of Staphylococcus aureus strain, comorbidity measured by Charlson WIC, and altered mental status on the day of SAB. Statistical analysis was performed using SAS version 8.2 (SAS Institute, Inc., Carey, NC).

Results

A total of 249 patients with SAB were identified and 142 of them were [greater than or equal to]60 years of age. Seven patients were not included in the study because of missing information or inability to locate the charts. A total of 135 elderly patients with SAB were included in the study and final analysis. The demographic and clinical characteristics of elderly patients with SAB are shown in Table 1. Most of the patients had underlying medical conditions; 62 (45.9%) patients had diabetes mellitus. Ten (16.1%) diabetic elderly patients were managed by diet as a mean of outpatient glycemic control. However, the majority of diabetic elderly were prescribed oral agents (32.3%), insulin (35.5%), or both oral agents and insulin (16.1%), as an outpatient therapy for diabetes. Fifty-eight patients had an HbA1c within 2 months of the onset of SAB with a mean of 6.9 [+ or -] 1.7. The mean blood glucose level 7 days post-SAB was 149.4 [+ or -] 48.6 mg/dL. Thirty-seven (27.4%) patients had a mean blood glucose 7 days post-SAB [greater than or equal to]170 mg/dL. Seventy-four cases (54.8%) of SAB were due to methicillin-resistant Staphylococcus aureus (MRSA). Nineteen patients (14.1%) had evidence of metastatic infection. Osteomyelitis/diskitis with and without epidural abscess was the most common site of metastasis followed by endocarditis. Forty-two (31.1%) patients had bacteremia other than Staphylococcus aureus during the same hospitalization and coagulase-negative Staphylococcus was the most common isolate followed by enterococci.

During the follow-up period from admission to discharge, 36 (26.7%) patients had died. Factors associated with increased mortality in elderly patients with SAB are shown in Table 1. There was a significant difference between the 7-day post-SAB mean blood glucose level among patients who survived and those who died (145.8 [+ or -] 46.8 mg/dL, 160.2 [+ or -] 52.2 mg/dL, P = 0.03). There were more patients with a 7-day post-SAB mean blood glucose level [greater than or equal to]170 mg/dL among the patients who died than those who survived (41.7%, 22.2%, P = 0.03). However, the mean HbA1c in both groups of patients were not different (P = 0.9). Patients who died had more comorbid conditions and more severe illness reflected by higher Charlson WIC and SAPS scores, respectively. Altered mental status at the onset of SAB was more common in patients who died than in patients who survived (P < 0.0001). Patients who died were more likely to have MRSA bacteremia than surviving patients (75.8%, 49.5%, P = 0.01). The timing of starting an effective anti-staphylococcal agent from the onset of SAB was no different between the survival and deceased groups (1.5 [+ or -] 1.7 days, 1.1 [+ or -] 1.6 days, P = 0.3, respectively).

Baseline characteristics of older adults with SAB, stratified by the degree of hyperglycemia after the onset of SAB, are displayed in Table 2.

Patients with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL were more likely to die compared with patients with a 7-day post-SAB mean blood glucose <170 mg/dL (P = 0.03). Fifteen (40.5%) patients with mean blood glucose levels [greater than or equal to]170 mg/dL died and 21 (21.4%) of patients with mean blood glucose levels <170 mg/dL died during the same hospitalization for the onset of SAB. Twenty-eight (75.7%) patients with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL had diabetes while 34 (34.7%) patients with a 7-day post-SAB mean blood glucose <170 mg/dL had diabetes (P < 0.0001). Patients with a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL had significantly more comorbid conditions, reflected by a higher mean Charlson WIC score, in comparison with patients with a 7-day post-SAB mean blood glucose <170 mg/dL (P = 0.01). However, the mean SAPS score at the onset of SAB was similar in both groups (P = 0.6). A multivariate analysis with a stepwise logistic regression model was used to identify the factors associated with death in elderly patients with SAB. P values of <0.2 and <0.05 were used for covariate inclusion and retention in the model, respectively. The final multivariate model identified 3 independent determinants of death; SAPS score at onset of SAB >45 (OR 5.3, 95% CI [1.8, 15.5], P = 0.002), a 7-day post-SAB mean blood glucose [greater than or equal to]170 mg/dL (OR 3.3, 95% CI [1.2, 9.1], P = 0.03), and altered mental status at the onset of SAB (OR 7.8, 95% CI [2.5, 23.9], P = 0.0003) (Table 3). Neither the appropriateness nor the timing of the antibiotic was a significant predictor of mortality among older patients with SAB.

Discussion

To our knowledge, this is the first study to investigate the association between the degree of hyperglycemia and mortality among elderly patients with SAB. It has shown that elderly patients with a 7-day post-SAB mean blood glucose level [greater than or equal to]170 mg/dL were 3.3 times more likely to die compared with elderly patients with a 7-day post-SAB mean blood glucose level <170 mg/dL. In addition, 40.5% of patients with mean blood glucose levels [greater than or equal to]170 mg/dL died, whereas 21.4% of patients with mean blood glucose levels <170 mg/dL died during the same hospitalization for the onset of SAB. The increased mortality among patients with a high mean blood glucose level and SAB might be due to abnormalities in neutrophil adherence, chemotaxis, phagocytosis, oxidative burst, and intracellular killing which occur in the state of hyperglycemia. (15) Neutrophils represent the host's first defense barrier against bacterial agents such as Staphylococcus aureus. Rayfield et al found a significant diminution of intracellular bactericidal activity of neutrophils in diabetic subjects for Staphylococcus aureus. They have also demonstrated that after controlling the blood glucose level, there was a significant improvement in the killing activity of neutrophils.16 Furthermore, proliferation of B cells in response to Staphylococcus aureus was significantly impaired in diabetic patients with hyperglycemia. Normalization of blood glucose with glyburide was associated with the return of normalized B cell proliferation in response to Staphylococcus aureus. (17)

Several studies have demonstrated that hyperglycemia increased the risk of nosocomial infection and glycemic control reduced the risk of infection. (9,18,19) However, few studies have reported the association between the degree of hyperglycemia and excess in hospital mortality among patients with infections. In a retrospective cohort study, we found that diabetic patients with a 7-day postcandidemia mean blood glucose level [greater than or equal to]250 mg/dL had a 6 eightfold increased risk of death compared with diabetic patients with a 7-day postcandidemia mean blood glucose level of <250 mgl/dL. Approximately two-thirds of patients with mean blood glucose levels [greater than or equal to]250 mg/dL died, whereas one-third of patients with mean blood glucose levels <250 mg/dL died during the same hospitalization for the onset of candidemia. (12) Leibovici et al (13) evaluated the effect of glycemic control, measured by HbA1c, on hospital mortality in diabetic patients with infection. The mortality in diabetics with nonfatal disease and low HbA1c was 2% versus 17% in patients with high HbA1c (P = 0.03). HbA1c above the median (OR 3.3, 95% CI [1.8-6.2]) was among the significant factors related to mortality in diabetics with infection. In the previous two studies, the patient population was a mixture of young and old diabetic adults. In our current study, we have included both diabetic and nondiabetic elderly patients. Furthermore, hyperglycemia was found to be a risk factor for an adverse outcome, defined as in-hospital death, intensive care unit admission, hospital length of stay >2 days, or hospital IV antibiotics >2 days, in elderly patients with urinary tract infection. (20)

Although our study failed to show an association between mortality and hypoglycemia, Van den Berghe et al (21) showed that hypoglycemia was an independent risk factor for death among patients admitted to a medical intensive care unit.

This study has several limitations. Because of the small sample size, we have stratified our study patients using a 7-day post-SAB mean blood glucose level into 2 groups of prognostic severity. In a retrospective cohort study of 1826 patients admitted to the intensive care unit, Krinsely (22) found that the hospital mortality increased progressively with further increases in mean blood glucose levels. The hospital mortality was 9.6% among patients with mean blood glucose levels between 79 and 99 mg/dL and the highest mortality, 42%, was among patients with mean glucose values exceeding 299 mg/dL. We did not study whether there was a difference in mortality between nondiabetic patients with hyperglycemia and diabetic patients. Umpierrez et al (10) found that patients with new hyperglycemia had higher in-hospital mortality (16%) than those with a known history of diabetes (3%) and normoglycemia (1.7%), both P < 0.01.

Since this is an observational study, a causal link between hyperglycemia and increased mortality cannot be established. Although we have adjusted for the severity of illness and comorbid conditions, patients with a mean blood glucose level [greater than or equal to]170 mg/dL had a higher mean Charlson WIC score. Finally, we did not study the effect of treatment in improving glucose control. In a randomized, controlled trial in mechanically ventilated patients who were admitted to a surgical intensive care unit, van den Berghe et al (9) reported a significant risk reduction of 43% (P = 0.036) in mortality among patients who were treated with intensive insulin therapy using continuous insulin infusion. It has also been demonstrated that achieving normoglycemia rather than the infused insulin dose was related to the beneficial effects of intensive insulin therapy in reducing mortality and morbidity of critically ill patients. (23)

In conclusion, as mortality increases with increasing age, it is particularly important to identify patients at risk within the geriatric population. Since hyperglycemia is an important predictor of increased mortality among elderly patients with SAB, good glycemic control with hypoglycemia avoidance should be considered for elderly patients with Staphylococcus aureus bacteremia.

References

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3. Van der Horst IC, Ligtenberg JJ, Bilo HJ, et al. Glucose-insulin-potassium infusion in sepsis and septic shock: no hard evidence yet. Crit Care 2003;7:13-15.

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5. McCowen KC, Malhotra A, Bistrian BR. Endocrine and metabolic dysfunction syndromes in the critically ill. Crit Care Clin 2001;17:107-124.

6. Volpi E, Ferrando AA, Yeckel CW, et al. Exogenous amino acids stimulate net muscle protein synthesis in the elderly. J Clin Invest 1998;101:2000-2007.

7. Fava S, Aquilina O, Azzopardi J, et al. The prognostic value of blood glucose in diabetic patients with acute myocardial infarction. Diabet Med 1996;13:80-83.

8. Norhammar AM, Ryden L, Malmberg K. Admission plasma glucose: independent risk factor for long-term prognosis after myocardial infarction even in nondiabetic patients. Diabetes Care 1999;22:1827-1831.

9. van den Berghe G, Wouters P, Weekers F, et al. Intensive insulin therapy in critically ill patients. N Engl J Med 2001;345:1359-1367.

10. Umpierrez GE, Isaacs SD, Bazargan N, et al. Hyperglycemia: an independent marker for in-hospital mortality in patients with undiagnosed diabetes. J Clin Endocrinol Metab 2002;87:978-982.

11. Clement S, Braithwaite SS, Magee MF, et al. Management of diabetes and hyperglycemia in hospitals. Diabetes Care 2004;27:553-591.

12. Bader M, Hinthorn D, Lai SM, et al. Hyperglycemia and mortality of diabetic patients with candidemia. Diabet Med 2005;22:1252-1257.

13. Leibovici L, Yehezkelli Y, Porter A. Influence of diabetes mellitus and glycemic control on the characteristics and outcome of common infections. Diabet Med 1996;13:457-463.

14. Rasaiah B. Self-monitoring of the blood glucose level: potential sources of inaccuracy. Can Med Assoc J 1985;132:1357-1361.

15. Pozzilli P, Leslie R. Infection and diabetes: mechanisms and prospects for prevention. Diabet Med 1994;11:935-941.

16. Rayfield E, Ault M, Keusch G, et al. Infection and diabetes: the case for glucose control. Am J Med 1982;72:439-450.

17. Alexiewicz JM, Kumar D, Smogorzewski M, et al. Elevated cytosolic calcium and impaired proliferation of B lymphocytes in type II diabetes mellitus. Am J Kidney Dis 1997;30:98-104.

18. Grey NJ, Perdrizet GA. Reduction of nosocomial infections in the surgical intensive-care unit by strict glycemic control. Endocr Pract 2004; 10 (Suppl 2):46-52.

19. Latham R, Lancaster A, Covington J, et al. The association of diabetes and glucose control with surgical-site infections among cardiothoracic surgery patients. Infect Control Hosp Epidemiol 2001;22:607-612.

20. Ginde AA, Rhee SH, Katz ED. Predictors of outcome in geriatric patients with urinary tract infections. J Emerg Med 2004;27:101-108.

21. van den Berghe G, Wilmer A, Hermans G, et al. Intensive insulin therapy in the medical ICU. N Engl J Med 2006;354:449-461.

22. Krinsley JS. Association between hyperglycemia and increased mortality in a heterogeneous population of critically ill patients. Mayo Clin Proc 2003;78:1471-1478.

23. van den Berghe G, Wouters PJ, Bouillon R, et al. Outcome benefit of intensive insulin therapy in the critically ill: insulin dose versus glycemic control. Crit Care Med 2003;31:359-366.

Mazen S. Bader, MD, MPH

From the Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK.

Reprint requests to Dr. Mazen S. Bader, Memorial University of Newfoundland Health Sciences Center, 300 Prince Phillip Drive, 1J426, St. John's, NL A1B3V6. Email: [e-mail].

Accepted August 23, 2006.

RELATED ARTICLE: Key Points

* Staphylococcus aureus bacteremia is associated with a high mortality in elderly patients.

* Since hyperglycemia is an important predictor of increased mortality among elderly patients with Staphylococcus aureus bacteremia, good glycemic control with avoiding hypoglycemia should be considered.

* Elderly patients are more likely to be infected with methicillin-resistant Staphylococcus aureus.

Table 1. Demographic characteristics, clinical characteristics, and
blood glucose levels in elderly patients with Staphylococcus aureus
bacteremia

                                        All patients    Survived
Characteristic                          (n = 135)       (n = 99)

Age (years)                              72.7 [+ or -]   71.9 [+ or -]
                                           7.8             7.6
Gender Male/Female                        6.9             7.3
Coronary artery disease                  52 (38.5%)      35 (35.4%)
Chronic lung disease                     47 (34.8%)      31 (31.3%)
Cancer                                   44 (32.6%)      27 (27.3%)
Congestive heart failure                 47 (34.8%)      31 (31.3%)
Cerebrovascular disease                  44 (32.6%)      36 (36.4%)
Chronic renal disease                    47 (34.8%)      36 (36.4%)
Diabetes mellitus                        62 (45.9%)      48 (48.5%)
Nosocomial SAB                           49 (36.3%)      32 (32.2%)
MRSA bacteremia                          74 (54.8%)      49 (49.5%)
Altered mental status at onset of SAB    63 (46.7%)      32 (32.2%)
SAPS score at onset of SAB
  SAPS score >45                         30 (22.2%)      10 (10.1%)
  Mean SAPS score                        37.9 [+ or -]   33.3 [+ or -]
                                           14.1            9.9
Mean Charlson WIC                         4.6 [+ or -]    4.3 [+ or -]
                                            2.6             2.5
Charlson WIC >5                          44 (32.6%)      26 (26.3%)
HbA1c (%)                                 6.9 [+ or -]    6.9 [+ or -]
                                            1.7             1.7
MBG 7 days post-SAB (mg/dL)             149.4 [+ or -]  145.8 [+ or -]
                                          48.6            46.8
MBG 7 days post-SAB                      37 (27.4%)      22 (22.2%)
  [greater than or equal to] 170 mg/dL
Hypoglycemia                             16 (11.9%)      12 (12.1%)
Appropriate antimicrobial therapy        70 (51.9%)      54 (54.6%)

                                        Died
Characteristic                          (n = 36)             P

Age (years)                              74.8 [+ or -] 8.2    0.09
Gender Male/Female                        6.2                 0.8
Coronary artery disease                  17 (47.2%)           0.2
Chronic lung disease                     16 (44.4%)           0.2
Cancer                                   17 (47.2%)           0.03
Congestive heart failure                 16 (44.4%)           0.2
Cerebrovascular disease                   8 (22.2%)           0.1
Chronic renal disease                    11 (30.6%)           0.5
Diabetes mellitus                        14 (38.9%)           0.3
Nosocomial SAB                           17 (47.2%)           0.1
MRSA bacteremia                          25 (75.8%)           0.01
Altered mental status at onset of SAB    31 (86.1%)          <0.0001
SAPS score at onset of SAB
  SAPS score >45                         20 (55.6%)          <0.0001
  Mean SAPS score                        50.6 [+ or -] 16    <0.0001
Mean Charlson WIC                         5.7 [+ or -] 2.8    0.01
Charlson WIC >5                          18 (50%)             0.01
HbA1c (%)                                 7.0 [+ or -] 1.6    0.9
MBG 7 days post-SAB (mg/dL)             160.2 [+ or -] 52.2   0.03
MBG 7 days post-SAB                      15 (41.7%)           0.03
  [greater than or equal to] 170 mg/dL
Hypoglycemia                              4 (11.1%)           1.0
Appropriate antimicrobial therapy        16 (44.4%)           0.3

Data expressed as mean [+ or -] SD or frequency and percentage as
indicated.
MBG, mean blood glucose; SAB, Staphylococcus aureus bacteremia; MRSA,
methicillin-resistant Staphylococcus aureus; Charlson WIC, Charlson
weighted index of comorbidity.

Table 2. Baseline characteristics of elderly patients with
Staphylococcus aureus bacteremia stratified by a 7-day post-SAB mean
blood glucose level

Characteristic            Patients with MBG <170 mg/dL (n = 98)

Age (years)               73.0 [+ or -] 8.2
Nursing home patients     28 (28.6%)
Coronary artery disease   32 (32.7%)
Chronic lung disease      40 (40.8%)
Chronic renal disease     29 (29.6%)
Diabetes mellitus         34 (34.7%)
MRSA bacteremia           57 (59.4%)
Altered mental status at  44 (44.9%)
  onset of SAB
Mean SAPS score           37.0 [+ or -] 12.4
Charlson WIC >5           26 (26.4%)
Mean Charlson WIC          4.4 [+ or -] 2.7
HbA1c (%)                  6.8 [+ or -] 1.2
Death                     21 (21.4%)

                          Patients with MBG
                          [greater than or equal to] 170 mg/dL
Characteristic            (n = 37)                              P

Age (years)               71.8 [+ or -] 6.8                      0.6
Nursing home patients      7 (18.9%)                             0.3
Coronary artery disease   20 (54.1%)                             0.02
Chronic lung disease       7 (18.9%)                             0.02
Chronic renal disease     18 (48.7%)                             0.04
Diabetes mellitus         28 (75.7%)                            <0.0001
MRSA bacteremia           17 (47.2%)                             0.2
Altered mental status at  19 (51.4%)                             0.5
  onset of SAB
Mean SAPS score           40.3 [+ or -] 17.7                     0.6
Charlson WIC >5           18 (48.7%)                             0.02
Mean Charlson WIC          5.4 [+ or -] 2.3                      0.01
HbA1c (%)                  7.1 [+ or -] 2                        0.4
Death                     15 (40.5%)                             0.03

Data expressed as mean [+ or -] SD or frequency and percentage as
indicated.
MRSA, methicillin-resistant Staphylococcus aureus; Charlson WIC,
Charlson weighted index of comorbidity.

Table 3. Risk factors associated with death among elderly patients with
Staphylococcus aureus bacteremia

Variable                                  Odd ratio  95% CI    P

SAPS score >45 at onset of SAB            5.3        1.8-15.5  0.002
MBG [greater than or equal to] 170 mg/dL  3.3        1.2-9.2   0.03
  7 days post-SAB
Altered mental status at onset of SAB     7.8        2.5-23.9  0.0003

MBG, mean blood glucose; SAB, Staphylococcus aureus bacteremia.