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Research question Is mild renal impairment an independent risk factor for cardiovascular disease in otherwise healthy adults?
Why did the authors do the study? People with chronic renal failure have an increased risk of cardiovascular disease. These authors wanted to find out the risks associated with much milder forms of renal impairment. More specifically, they wanted to know how low glomerular filtration rate (GFR) has to fall before cardiovascular risk begins to rise in otherwise healthy adults.
What did they do? They selected 8913 participants without cardiovascular disease or diabetes from an original cohort of 30Â 000 adults chosen at random from the Belgian electoral register and followed them up for 10 years after baseline assessments of their GFR and cardiovascular risk factors. The authors recorded all deaths during follow-up and used death certificates and hospital notes to ascertain the causes of death. They looked for an association between GFR at baseline and risk of death from cardiovascular disease, adjusting the results for age, sex, body mass index, smoking, mean arterial blood pressure, serum concentration of total cholesterol, and serum concentration of uric acid.
What did they find? In these apparently healthy adults, even mild renal impairment was associated with a significantly increased risk of dying from cardiovascular disease. When the authors divided participants by quartiles of GFR, those in the bottom two categories (GFR <89.4 ml/min/1.73m2) were more than twice as likely to die from cardiovascular disease compared with those in the top quarter (GFR >104.3 ml/min/1.73m2). The hazard ratios for death from cardiovascular disease were 2.48 (95% CI 1.26 to 4.87) for those with a GFR of 75.6-<89.4 ml/min/1.73m2 and 2.21 (1.13 to 4.32) for those with a GFR <75.6 ml/min/1.73m2.
The effect of mild renal impairment on cardiovascular risk was about the same for men and women and was independent of age and traditional cardiovascular risk factors including smoking. The authors estimate that cardiovascular risk goes down by 8% for every 10 ml/min/1.73m2 increase in GFR (hazard ratio 0.92 (0.85 to 0.99)).
What does it mean? Renal impairment seems to have a detrimental effect on cardiovascular risk at an early stage, even among apparently healthy adults. This study suggests that risk starts to rise once GFR falls below about 90 ml/min/1.73m2, a substantially higher cut-off point than previous estimates and one that the authors describe as “near normal.”