Impaired renal function linked to increased CVD death in women

3 July 2009

MedWire News: Study findings suggest there is no link between mild-to-moderate kidney impairment and increased risk for cardiovascular disease (CVD) or mortality in women without existing major disease.

However, the data point to an increased risk for CVD death, but not other CVD or mortality outcomes, among women with impaired kidney function, a finding the authors say “deserves further investigations.”

CVD and kidney disease are closely related, with CVD risk factors highly prevalent in people with impaired kidney function and predictive of chronic kidney disease. Studies consistently showing people with impaired kidney function are at increased risk for CVD and death have been limited to populations already at high risk for CVD, with existing CVD, or with severely impaired kidney function, however.

To investigate further, Tobias Kurth, from Harvard Medical School in Boston, Massachusetts, USA, and colleagues studied prospective data for 27,939 participants of the Women’s Health Study, a randomized trial of low-dose aspirin and vitamin E supplements in nearly 40,000 relatively healthy, predominantly White, female healthcare professionals aged 45 years or older.

The researchers used participants’ serum creatinine measurements to calculate estimated glomerular filtration rate (GFR) using the four-variable Modification of Diet in Renal Disease (MDRD) Study equation.

As reported in the British Medical Journal, there were 1199 CVD events and 856 deaths over a mean of 12 years. Kurth and team found no association between GFR categories and risk for any CVD event or death from any cause.

Compared with women with an estimated GFR ≥90 ml/min/1.73 m², those with an estimated GFR <60ml/min/1.73 m² had a significantly increased risk for CVD death, at a hazard ratio of 1.68. No significant linear trend in risk for CVD death was seen across GFR categories, however.

In an accompanying editorial, Daniel Wiener and Dena Rifkin, from Tufts Medical Center, also in Boston, say that well-known limitations in creatinine measurement, particularly at low creatinine levels, could have introduced misclassification bias in the current study population, as the values may not be appropriately calibrated for use in the MDRD equation.

This may at least partly account for an apparent J-shaped association between GFR and CVD death and all-cause death, they say.

Furthermore, they note that the lack of effect on all-cause mortality is unsurprising given that GFR estimates are less accurate at higher levels and when the likelihood of kidney disease is low.

Nevertheless they conclude: “The finding of increased mortality from cardiovascular disease, despite inaccuracies in measurement and the presence of a J-shaped association, suggest that better measures of early loss of kidney function might help detect increased risk associated with chronic kidney disease, even in healthy people.”

MedWire is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

Br Med J 2009; 338: b2392