Proteinuria as a risk factor for cardiovascular disease and mortality in older people: a prospective study

Differential effects of calcium antagonist subclasses on markers of nephropathy progression

BACKGROUND

Numerous studies suggest that the dihydropyridine calcium antagonists (DCAs) and nondihydropyridine calcium antagonists (NDCAs) have differential antiproteinuric effects. Proteinuria reduction is a correlate of the progression of renal disease. In an earlier systematic review, calcium antagonists were shown as effective antihypertensive drugs, but there was uncertainty about their renal benefits in patients with proteinuria and renal insufficiency.

METHODS

A systematic review was conducted to assess the differential effects of DCAs and NDCAs on proteinuria in hypertensive adults with proteinuria, with or without diabetes, and to determine whether these differential effects translate into altered progression of nephropathy. Studies included in the review had to be randomized clinical trials with at least 6 months of treatment, include a DCA or NDCA treatment arm, have one or more renal end points, and have been initiated after 1986. Summary data were extracted from 28 studies entered into two identical but separate databases, which were compared and evaluated by independent reviewers. The effects of each drug class on blood pressure (N= 1338) and proteinuria (N= 510) were assessed.

RESULTS

After adjusting for sample size, study length, and baseline value, there were no statistically significant differences in the ability of either class of calcium antagonist to decrease blood pressure. The mean change in proteinuria was +2% for DCAs and -30% for NDCAs (95% CI, 10% to 54%, P= 0.01). Consistently greater reductions in proteinuria were associated with the use of NDCAs compared with DCAs, despite no significant differences in blood pressure reduction or presence of diabetes.

CONCLUSION

This analysis supports (1) similar efficacy between subclasses of calcium antagonists to lower blood pressure, and (2) greater reductions in proteinuria by NDCAs compared to DCAs in the presence or absence of diabetes. Based on these findings, NDCAs, alone or in combination with an angiotensin-converting enzyme (ACE) inhibitor or an angiotensin receptor blocker (ARB), are suggested as preferred agents to lower blood pressure in hypertensive patients with nephropathy associated with proteinuria.

Ethnic differences and determinants of proteinuria among South Asian subgroups in Pakistan

BACKGROUND

Hypertension, diabetes, increasing age, and smoking are known risk factors for proteinuria. Prevalence of proteinuria is high in South Asians. However, ethnic subgroup differences and determinants of proteinuria within the South Asian population have not been explored.

METHODS

The National Health Survey of Pakistan conducted between 1990 and 1994 was used to explore ethnic subgroup variation in proteinuria. Distinct ethnic subgroups, the Muhajir, the Punjabi, the Sindhi, the Pashtun, and the Baluchi, were defined by mother tongue. We report results in individuals aged >or=15 years (N = 9442). Proteinuria was defined as dipstick positive for protein on random urine sample.

RESULTS

Increasing age, high consumption of meat, and presence of hypertension and diabetes were each independently associated with proteinuria. The age-standardized prevalence of proteinuria was 4.6% (4.2% to 5.1%) and varied among ethnic subgroups (P < 0.001). The highest was among the Sindhi (men 9.5%, women 10.3%), then the Muhajir (men 8.2%, women 4.7%), the Punjabi (men 3.2% women 3.5%), and lowest among the Baluchi (men 2.4%, women 4.2%) and the Pashtun (men 2.7%, women 1.2%). The ethnic differences persisted after adjusting for the above-mentioned sociodemographic, dietary, and clinical risk factors [adjusted odds ratio (OR) (95% CI)] were 6.42 (3.97 to 10.38) for the Sindhis, 3.58 (2.22 to 5.79) for the Muhajirs, 2.03 (1.25 to 3.29) for the Punjabis, and 1.75 (0.79 to 3.88) for the Baluchis compared to the Pashtuns).

CONCLUSION

We conclude that unmeasured environmental or genetic factors account for ethnic variations in proteinuria, and deserve further study.

Proteinuria and the risk of developing end-stage renal disease

BACKGROUND

Dipstick urinalysis for proteinuria and hematuria has been used to screen renal disease, but evidence of the clinical impact of this test on development of end-stage renal disease (ESRD) is lacking.

METHODS

We assessed development of ESRD through 2000 in 106,177 screened patients (50,584 men and 55,593 women), 20 to 98 years old, in Okinawa, Japan, who participated in community-based mass screening between April 1983 and March 1984. We used data from the Okinawa Dialysis Study Registry to identify ESRD patients. Multivariate logistic analyses were performed to calculate adjusted odds ratio and 95% confidence interval (95% CI) for the significance of proteinuria and hematuria on the risk of developing ESRD with confounding variables such as age, gender, blood pressure, and body mass index. A similar analysis was repeated in a subgroup of screened patients in whom serum creatinine data existed.

RESULTS

During 17 years of follow-up, 420 screened persons (246 men and 174 women) entered the ESRD program. We identified a strong, graded relationship between ESRD and dipstick urinalysis positive for proteinuria; adjusted odds ratio (95% CI) was 2.71 (2.51 to 2.92, P < 0.001). Similar trends were observed after adding serum creatinine data. Compared with dipstick-negative proteinuria, adjusted odds ratio (95% CI) of proteinuria (1+) was 1.93 (1.53 to 2.41, P < 0.001) in men and 2.42 (1.91 to 3.06, P < 0.001) in women.

CONCLUSION

Proteinuria was a strong, independent predictor of ESRD in a mass screening setting. Even a slight increase in proteinuria was an independent risk factor for ESRD. Therefore, asymptomatic proteinuria warrants further work-up and intervention.

Applying multiple interventions in chronic kidney disease

The medical, social, and financial burdens posed by end-stage renal disease (ESRD) are many and growing rapidly. People generally reach ESRD as a result of chronic progressive kidney disease. Advancing kidney disease is associated with several treatable complications, which if poorly managed reduce the length and quality of life. In addition, there are strong links between chronic kidney disease (CKD) and cardiovascular disease (CVD). Many people with less advanced CKD will die or suffer complications of CVD before reaching ESRD. Efficacious interventions, such as lowering blood pressure and treating dyslipidemia, can substantially reduce the progression of both kidney and cardiovascular disease. Careful management of these complex and interrelated diseases and risk factors requires detailed longitudinal and focused care which does not seem to be optimally delivered by health service practitioners organized in traditional ways. A disease management approach offers promise in this setting, but requires further study of clinical and economic impact.

Influence of smoking and obesity on the development of proteinuria

BACKGROUND

Proteinuria is a significant risk factor for end-stage renal disease. Previous evidence suggested that smoking and obesity increase the risk of proteinuria. However, it is unclear whether these risk factors predict the development of proteinuria independently of hypertension and diabetes mellitus. The aim of this study was to analyze the effects of obesity and smoking on the development of proteinuria in a screened cohort of subjects with normal kidney function.

METHODS

A total of 5403 subjects (3403 men and 2000 women) who participated in the 1997 and 1999 health screening examinations in Okinawa Japan, and who were normal renal function (serum creatinine < or =1.2 mg/dL in men, < or =1.0 mg/dL in women) and negative proteinuria by dipstick examination in 1997 were eligible for study. Logistic analysis was used to examine the relation between the baseline state of smoking or obesity in 1997, and the development of proteinuria in 1999, adjusted for age, sex, and other confounding factors.

RESULTS

Proteinuria developed in 5.8% of participants (6.7% in men, 4.4% in women; dipstick score, 1+ in 277, 2+ in 37, and > or =3+ in 4 participants). The incidence of proteinuria was positively associated with the number of cigarettes smoked per day (P = 0.04), and a body mass index (P < 0.0001) at baseline. Analysis showed that the relative risk (95% confidence interval) of developing proteinuria was 1.32 (1.00 to 1.74), P = 0.04 for cigarette smoking, 1.45 (1.13 to 1.86), P = 0.002 for obesity, 1.56 (1.19 to 2.06), P = 0.001 for hypertension, and 2.27 (1.55 to 3.32), P < 0.0001 for diabetes mellitus. Stratified with men and women, the relative risk was 1.28 (0.96 to 1.72), P = 0.09 for smoking, and 1.60 (1.19 to 2.14), P = 0.001 for obesity in men; the relative risk was 1.30 (0.44 to 3.80), P = 0.62 for smoking, and 1.04 (0.63 to 1.72), P = 0.87 for obesity in women.

CONCLUSIONS

Hypertension and diabetes mellitus were superior to smoking and obesity in predicting the development of proteinuria in all subjects. Stratified with men and women, obesity was a significant risk factor for the development of proteinuria independently of both hypertension and diabetes mellitus in men. The risk of developing proteinuria also tended to be increased with cigarette smoking in men. Smoking and obesity in women were not significant in this data set.

Primary renal disease as a cardiovascular risk factor

Cardiovascular disease (CVD) is the No. 1 cause of death in patients with end-stage renal disease (ESRD) and is approximately 3 to 5 times that of non-uremic control subjects. Moreover, higher rates of CVD are seen in patients with moderate and even mild renal dysfunction, particularly if the patient has hypertension or diabetes. Recent studies have indicated that even modest elevations in serum creatinine and urinary albumin excretion are associated with increased CVD risk, not only in persons with diabetes or hypertension but also in the general population. In addition, recent studies have suggested that targeting the kidney and/or kidney specific endpoints (via the renin-angiotensin-aldosterone-kinin system) in the treatment of hypertension, diabetes, and heart failure slows progression of renal disease and reduces the risk of extra-renal micro- and macrovascular complications. We conclude that it is important to screen for renal disease in those with hypertension, diabetes, and other CVD risk factors because it predicts those who are at high risk for major CVD events.