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Diabetes, Kidney Problems and Cardiovascular Risk in Minority Patients

Prevalence of early CKD higher among Hispanics and African Americans.

Non-communicable diseases (NKDs) are becoming responsible for more morbidity and premature death than communicable diseases. This has led to massive losses of human investment and high health care spending. It is projected that cardiovascular (CV) disease and diabetes together will reduce global gross domestic product by 5%. Increasing rates of diabetes mellitus throughout the developed world represent an evolving epidemic with profound concerns. Approximately 30% of patients with diabetes mellitus develop chronic kidney disease (CKD) accounting for 45% of end stage renal disease (ESRD). African Americans and Hispanics have had incidence of new ESRD of 3.4 and 1.8 per 2012 United States Renal Data System report. The incidence of ESRD attributed to DM or hypertension was found to be 12 times higher among African Americans as compared to whites. In general population, however, the prevalence of early CKD was not elevated in minorities. CV disease is a common complication of ESRD and diabetes and is responsible for high mortality in these patients. Although a lot of resources have been spent on efforts to reduce the incidence of CV events in these patients, they still face poor outcomes of CV events. Inflammation is known to play a vital role in renal diseases. Studies even recommend that inflammatory mechanisms significantly contribute to the development and progression of CKD. C- reactive protein (CRP) is linked with microalbuminuria in diabetic patients.

The purpose of this study is to investigate whether African Americans and Hispanics have a higher prevalence of early CKD in patients with primarily type 2 DM. The National Health and Nutrition Examination Survey was analyzed. There were 2,310 diabetic patients who were aged ≥ 20 years, of these, n = 693 with early CKD and those with no CKD n = 1,459. Data on race were collected through self-report and subjects classified as AA (n=647), Hispanics (n=799), white (n= 864) and Asian or other (n=91). Data were also analyzed based on history of hypertension, cardiovascular disease (CVD), smoking, and use of metformin, pioglitazone, statin, ACE inhibitors (ACEIs), systolic and diastolic blood pressure and many more. They were categorised as being obese or non-obese according to their BMI. They were also classified according to eGFR and (urinary albumin excretion) UAE. Descriptive statistics were used to characterize subjects. Student t test was used for continuous variables. Multiple linear regression models were used to adjust for confounding variables. Multiple logistics regression was used to determine the association between race and in both CRP and UAE.

Of the 2,310 subjects with type 2 diabetes, 864 were white, 647 were AA and 799 were Hispanics. 65% had hypertension, 19% had prevalent CVD and 27% were smokers. AA had higher levels of SBP, DBP, BMI, HbA1c and HDL-C, but lower serum triglyceride levels compared with whites and Hispanics (P< 0.01). Relative to white subjects and AAs, Hispanics had a lower prevalence of CVD, uric acid, and history of smoking (P<0.01). AAs had higher CRP and fibrinogen levels (P<0.01 and P<0.05, respectively) and lower WBC levels (P<0.01) relative to whites and Hispanics. Most importantly, AAs had higher serum creatinine compared with Hispanics or whites. Serum creatinine levels were slightly lower in diabetic patients with UAE ≥ 30 µg/ml (P<0.04). Macroalbuminuria had statistically significant higher levels of SBP, HbA1c and uric acid and higher reported history of hypertension but lower serum albumin (P<0.05). Microalbuminuria was present in 24% of white subjects, 27% of AA and 27% of Hispanics, whereas macroalbuminuria was in only 3% of white subjects, 10% of AAs and 7% of Hispanics.

UAE among people with early CKD was significantly elevated in AAs compared with whites. Hispanics had higher adjusted odds of UAE ≥30 µg/mL compared with whites, whereas the trend towards higher odds for UAE ≥30 µg/mL among AA did not reach statistical significance. In a multiple linear regression model it was found that there was a modest relationship between UAE and CRP for AA, and a more robust one for Hispanics. It also indicated that uric acid and not WBC was a significant predictor of UAE. Recent investigations suggest that type 2 diabetes includes an inflammatory component that significantly contributes to the origin and development of CKD. Some limitations of this study include the fact that it was a cross-sectional study and can only provide associations and not causation. Also, data on race was self- reported.

In conclusion, patients with DM and early CKD had increased CRP levels compared with those with DM and no CKD, also AAs and Hispanics had a higher prevalence of early CKD compared with whites.

Practice Pearls:

  • Increasing rates of diabetes mellitus throughout the developed world represent an evolving epidemic with profound concerns. Approximately 30% of patients with diabetes mellitus develop chronic kidney disease (CKD) accounting for 45% of end stage renal disease (ESRD).
  • Inflammation is known to play a vital role in renal diseases. Studies even recommend that inflammatory mechanisms significantly contribute to the development and progression of CKD. C- reactive protein is linked with microalbuminuria in diabetic patients.
  • African Americans and Hispanics had a higher prevalence of early CKD compared with whites.

 

References

Carter JS et al. “Non- insulin- dependent diabetes mellitus in minorities in the united states” Ann Intern Med 1996; 125:221-232.Web June 30 2016.

Tarver-Carr ME, et al. “Excess risk of chronic kidney disease among African-American versus white subjects in the United States: a population based study of potential explanatory factors.” J Am Soc Nephrol 2002; 13:2363-2370. Web 30 2016

Levey AS, et al. “National Kidney Foundation Practice Guidelines for Chronic Kidney Disease: evaluation, classification, and stratification”. Ann Intern Med 2003: 139:137-147. Web 30 2016