Low birth weight may raise kidney disease risk

NEW YORK (Reuters Health) - People who were born at a low weight may have an increased risk of eventually developing kidney disease, a research review suggests.

A number of studies have linked low birth weight to heightened risks of various adulthood health problems, including high blood pressure, diabetes and possibly chronic kidney disease. Overall, about 10 to 15 percent of adults are affected by chronic kidney disease.

One theory is that restricted growth during fetal development -- whether due to poor nutrition or some other factor -- can "program" certain organs or body systems to be more vulnerable to disease later in life.

Some researchers speculate that low-birth-weight infants -- those weighing less than 5.5 pounds at birth -- may become susceptible to kidney disease as adults because they have fewer and smaller kidney structures called nephrons. Normally, each kidney has roughly one million nephrons, which are the basic filtering units of the kidneys, extracting waste from the blood and producing urine.

"There has been great interest in the hypothesis that chronic kidney disease might have it origins in early life, and over the past two decades numerous studies have attempted to quantify the strength of associations between size at birth and markers of kidney function,"

Sarah L. White, the lead researcher on the new review, told Reuters Health in an email.

The review, which looked at 32 studies, is the first to systematically draw together the epidemiological evidence on the topic, said White, a researcher at the George Institute for International Health in Sydney, Australia.

Overall, she said, there was a "consistent association" between low birth weight and increased risk of impaired kidney function and kidney failure. In general, low-birth-weight babies were 70 percent more likely than normal-weight newborns to eventually develop chronic kidney disease.

In addition, when White's team looked at two large studies of twins, they found that when one twin was born weighing significantly less than the other, the smaller sibling tended to have poorer kidney function later in life.

The findings are published in the American Journal of Kidney Diseases.

The results, White said, support the idea that fetal growth restriction may eventually make the kidneys more vulnerable to dysfunction. But that is not to say that people born at a low weight are destined to develop kidney problems.

Maintaining a healthy weight is important, White noted, as that odds of developing type 2 diabetes, one of the major risk factors for kidney disease. A healthy diet and regular exercise also help control high blood pressure, another main contributor to kidney problems.

White also stressed the importance of regular medical check-ups. Routine measures, like blood pressure checks and urine and blood tests, can detect early kidney trouble.

SOURCE: American Journal of Kidney Diseases, August 2009.