Low birth weight linked to kidney disease in men

There appears to be an association between low birth weight and chronic kidney disease in adulthood in men, but this relationship was not seen in women, a new study has found.

It has been hypothesized that low birth weight leads to increased blood pressure, or "hypertension," and chronic kidney disease in adult life, Dr. A. J. Collins, of the Chronic Disease Research Foundation, Minneapolis, Minnesota, and colleagues, point out in their study, published in the journal Kidney International.

Evidence has also shown a direct relationship between birth weight and the number of nephrons in the kidney, they note. A nephron is one of about one million tubes that form the basic functional unit of the kidney, extracting waste from the blood and producing urine.

To investigate, the researchers used data from the National Kidney Foundation's Kidney Early Evaluation Program, a free community-based screening program for chronic kidney disease enrolling subjects at least 18 years of age with diabetes, hypertension, or a family history of kidney disease, diabetes, or hypertension.

A total of 12,364 participants, average age of 49.1 years, were included in the study. Overall, 28.7 percent were African American, 76.4 percent were female, and 15 percent had a birth weight less than 2500 grams.

The team categorized the subjects' birth weights into one of five groups, ranging from less than 2500 grams (about 5.50 pounds) to more than 4500 grams (about 10 pounds).

The researchers found that men with birth weights of less than 2500 grams were 65 percent more likely to have chronic kidney disease than those with normal birth weights. On the other end of the spectrum, men with birth weights of 4500 grams or more were 41 percent more likely to have chronic kidney disease. A similar relationship was not observed among the women.

"Studies on the association of birth weight and chronic kidney disease, and whether factors such as socioeconomic status and hypertension control could attenuate this association, may be needed," Collins' team concludes.

In addition, efforts must be made to understand the cause of the association between birth weight and chronic kidney disease, and to identify influential factors to improve public health.

SOURCE: Kidney International, March 2008.