Age, blood pressure and smoking effects on chronic renal failure in primary glomerular nephropathies

Background. Smoking is a known risk factor for renal damage in diabetic patients, but its relationship to other renal diseases is less clear. To assess its effect in primary glomerular nephropathy (GN), we used data from a case control study designed to assess several environmental risk factors. Methods. This study included 295 biopsy-proven GN cases, 80 membranous nephropathy, 116 IgA nephropathy, and 99 nephrotic syndrome with either minimal change nephropathy or focal segmental hyalinosis, and 242 matched hospital controls, with diseases unrelated to smoking. Subjects were interviewed about their smoking history. Chronic renal failure (CRF), defined by serum creatinine >150 mu mol/L, was present in 74 cases (57 men and 17 women). Logistic regression was used to estimate odds ratios (ORs) adjusted for age and social class. Results. In men, the percentage of ever-smokers did not differ between GN cases (60%) and controls [65%, OR = 0.9 (95% Confidence Interval 0.6-1.4)],but was significantly higher among cases with CRF (75%) than those without [55%, OR = 2.4 (1.24.5)]. Dose-effect relationships were observed with both the daily and cumulative dose; this relationship was stronger in the comparison of cases with CRF and those without CRF than in the comparison of cases with CRF with controls: OR = 1.9 versus 1.3 (less than or equal to 20 cigarettes/day) and OR = 5.2 versus 3.0 (>20 cigarettes/day); OR = 1.9 versus 1.4 (less than or equal to 15 pack years) and OR = 3.9 vs. 2.0 (>15 pack years). Interactions between age, hypertension, and smoking were observed in the risk of CRF: smoking was significantly related to CRF among cases who were older than 40 years and/or hypertensive, but not among those cases younger than 40 or normotensive. The results did not significantly differ among the three histologic types. No relationship was shown between smoking and CRF in women. Conclusion. This study provides additional support for the hypothesis that smoking is related to GN severity, particularly in the at-risk groups of men older than 40 and/or hypertensive patients. These findings should be corroborated by further observations in other populations.