Kidney Disease Linked to Modifiable Lifestyle Factors

Kate Johnson

May 05, 2011

May 5, 2011 (Las Vegas, Nevada) — The combination of obesity, smoking, poor diet, and lack of exercise can increase a person's risk for kidney disease by more than 300%, independent of age, sex, and race, according to research presented here at the National Kidney Foundation 2011 Clinical Meetings.

What is not clear is whether losing the bad habits can reverse the risk, so it is better to never develop them at all, said study investigator Alexander Chang, MD, from Loyola University Medical Center in Maywood, Illinois.

"By the time we see these patients, as nephrologists, it is already too late and they already have hypertension, diabetes, and kidney disease. It's hard to modulate these lifestyle factors after they've already occurred and caused all this damage," he told Medscape Medical News.

The study was an analysis of data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, in which cardiovascular risk factors in black and white adults, 18 to 30 years of age at baseline (1985/86), were followed for 20 years.

Participants with baseline hypertension, diabetes, or kidney disease were excluded from the analysis. In all, 2762 subjects were assessed at 10, 15, and 20 years for chronic kidney disease (CKD).

CKD was defined as incident persistent presence of microalbuminuria (defined as an albumin/creatinine ratio of 25 mg/g or more after adjustment for sex and race), or an estimated glomerular filtration rate of less than 60 mL/min per 1.732.

Each participant was assessed for body mass index (BMI), physical activity, and smoking history, and each completed a diet questionnaire that measured quantitative food frequency over the previous 28 days and assigned a score based on the DASH (Dietary Approaches to Stop Hypertension) diet, which emphasizes high intake of fruits, vegetables, low-fat dairy products, nuts, and whole grains, and low intake of sodium, sugar-sweetened beverages, and red and processed meats.

Over the course of the study, 97 subjects developed persistent microalbuminuria; obesity (defined as a BMI of 30 kg/m2 or higher), poor DASH diet score, and current smoking occurred significantly more frequently in this group than in those without microalbuminuria.

At 10- and 15-year follow-ups, after adjustment for age, sex, and race, significant multivariate predictors of microalbuminuria were the modifiable factors of obesity (odds ratio [OR], 2.75; P < .01) and poor diet (OR, 1.58; P < .05), and the nonmodifiable factors of diabetes (OR, 9.43; < .001) and hypertension (OR, 4.07; P < .001).

"Most of the obesity looks like it is mediated through the development of hypertension or diabetes during the course of the study, which is as you would expect because most of the increase in hypertension and diabetes risk seems to be due to the increasing rates of obesity in the country," said Dr. Chang.

There was also a trend, which did not reach significance, for a contribution to CKD risk of smoking (OR, 1.44) and sedentary lifestyle (OR, 1.25).

Although obesity and poor diet conferred 58% of the risk, individuals with 3 or 4 unhealthy lifestyle behaviors had a 337% increased risk for CKD, compared with those with no unhealthy behaviors.

The findings point to the need to encourage healthy lifestyle behaviors before the development of kidney disease, "to prevent not only kidney disease, but cardiovascular disease and cancer as well," said Dr. Chang.

Asked to comment on the study, Jeffrey Berns, MD, professor of medicine and pediatrics at the University of Pennsylvania School of Medicine in Philadelphia, said he is not optimistic about this approach.

"If we haven't been able to get people to lose weight and stop smoking because of lung cancer, heart attacks, and diabetes, which are very vivid diseases to some extent, I'm pretty sure that talking to them about the risk of these things for kidney disease is going to have even less of an impact," said Dr. Berns.

Additionally, although the study found an association between unhealthy lifestyle and kidney disease, there's no proof that lifestyle modification is preventive, he said in an interview. "It's good medical advice — exercise, don't get fat, watch your salt intake — for lots of different reasons: it reduces diabetes, it reduces lung cancer, it controls blood pressure. There's certainly no harm in adding that there may be potential implications for kidney disease on top of that, but we don't know that it prevents kidney disease."

Dr. Chang has disclosed no relevant financial relationships. Dr. Berns reports serving as an advisor or consultant to Amgen, Affymax, GlaxoSmithKline, Wyeth Pharmaceuticals, and Litholink; and receiving grants for clinical research from NxStage.

National Kidney Foundation (NKF) 2011 Clinical Meetings: Abstract 61. Presented April 28, 2011.

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