Progression to Overt Nephropathy in Type 2 Diabetes
The Casale Monferrato Study
- Graziella Bruno, MD1,
- Franco Merletti, MD2,
- Annibale Biggeri, MD3,
- Giuseppe Bargero, MD4,
- Stefania Ferrero, MD1,
- Gianfranco Pagano, MD1 and
- Paolo Cavallo Perin, MD1
- 1Department of Internal Medicine, Turin University, Turin, Italy
- 2Unit of Cancer Epidemiology, Turin University, Turin, Italy
- 3Department of Statistics G. Parenti, Florence University, Florence, Italy
- 4Santo Spirito Hospital, Casale Monferrato, Alessandria, Italy
- Address correspondence and reprint requests to Dr. Graziella Bruno, Department of Internal Medicine, Turin University, corso Dogliotti 14, I-10126 Torino, Italy. E-mail: graziella.bruno{at}katamail.com.
Abstract
OBJECTIVE—The first sign of diabetic nephropathy is microalbuminuria, but its predictive role of progression to overt nephropathy in type 2 diabetes has not yet been clarified. The aims of this study were to assess during 7 years of follow-up the incidence rate of overt nephropathy and the predictive role of microalbuminuria and other baseline variables (blood pressure, lipids, fibrinogen, uric acid, smoking, and HbA1c cumulative average during follow-up).
RESEARCH DESIGN AND METHODS—A prospective population-based study was performed in Casale Monferrato, Italy, including 1,253 type 2 diabetic patients recruited at baseline (1991–1992), 765 with normoalbuminuria (albumin excretion rate [AER] <20 μg/min) and 488 with microalbuminuria (AER 20–200 μg/min). All measurements were centralized. A nested case-control study within the cohort was performed, selecting four control subjects, frequency matched for age and attained individual time of follow-up with each case. Conditional regression analysis was performed to assess variables independently associated with risk of progression to overt nephropathy.
RESULTS—Of 1,253 total patients, 1,103 (88.0%) were included in the follow-up examination (median 5.33 years); their age and duration of disease at baseline were 68.4 ± 10.5 years and 10.4 ± 6.6 years, respectively. Cases of overt nephropathy were 202, giving an incidence rate of 37.0/1,000 person-years (95% CI 32.3–42.6). In conditional logistic regression analyses, microalbuminuria provided a 42% increased risk with respect to normoalbuminuria (95% CI 0.98–2.06), independently of duration of diabetes, hypertension, and systolic blood pressure. Other variables independently associated with progression to overt nephropathy were HbA1c cumulative average (P = 0.002), apolipoprotein B (P = 0.013), fibrinogen (P = 0.02), and HDL cholesterol (P = 0.03).
CONCLUSIONS—Of type 2 diabetic patients, 3.7% progress every year to overt nephropathy. Microalbuminuria is associated with a 42% increased risk of progression to overt nephropathy. Other independent predictors are HbA1c, HDL cholesterol, apolipoprotein B, and fibrinogen.
- AER, albumin excretion rate
- apo, apolipoprotein
- CHD, coronary heart disease
- ECG, electrocardiogram
- ESRD, end-stage renal disease
Footnotes
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A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
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- Accepted April 9, 2003.
- Received October 1, 2002.
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