Obese kids at risk for kidney disease as adults

By Charlene Laino

Avoiding excess weight gain in childhood and young adulthood could prevent many cases of chronic kidney disease later in life, researchers reported.

“A study of over 5,000 children born in 1946 found that more than one-third of chronic kidney disease cases at age 60 to 64 years in the United States could be avoided if nobody became overweight until at least that age,” reported Richard Silverwood, Ph.D., of the London School of Hygiene & Tropical Medicine, and colleagues.

The findings appear in the Journal of the American Society of Nephrology.

Obesity in childhood and early adulthood has previously been linked to a host of other problems, including heart disease and diabetes.

The new findings send a clear message to clinicians, said Janice Lea, M.D., a nephrologist at Emory University in Atlanta.

“Evidence is accumulating that obesity at younger ages is a clear factor for diabetes. What this means is that obese patients, whether diabetic or not, should be screened for kidney disease, starting with blood and urine workups,” Lea said in an interview. She was not involved with the study.

The findings come at a time when obesity among both children and adults has reached epidemic proportions. In 2008, more than 1.4 billion adults worldwide were overweight, with approximately 500 million of them being obese, according to the World Health Organization.

While other studies have suggested an association between being obese and kidney disease, the British researchers went a step further to determine the impact of becoming overweight and the duration of obesity on kidney disease risk.

They analyzed information from the Medical Research Council National Survey of Health and Development, a sample of children born in one week in March 1946 in England, Scotland, and Wales. Data, A total of 4,584 participants had available data, including body mass index at ages 20, 26, 36, 43, 53, and 60-64 years.

Among the findings:

  • Participants who were overweight beginning early in adulthood (ages 26 or 36 years) were twice as likely to have CKD at age 60-64 years compared with those who first became overweight at age 60-64 years or never became overweight.
  • The strength of this association decreased with increasing age when first becoming overweight (P for trend <0.001).
  • Larger waist-to-hip ratios at ages 43 and 53 years were also linked with CKD at age 60-64 years.

The analyses were adjusted for childhood and adulthood social classes.

CKD was defined by an estimated glomerular filtration rate (eGFR) of less than 60 ml/min per 1.73 mand/or urine albumin-to-creatinine ratio (UACR) of 3.5 mg/mmol or greater.

The link between overweight and CKD was only partly explained by taking diabetes and hypertension into account.

“Although we were unable to disentangle precisely whether it was the timing of overweight onset or the duration of overweight that was driving this association, either explanation suggests that preventing overweight in early adulthood may have a considerable effect on the prevalence of CKD in the population,” they wrote.

The authors concluded that the childhood obesity-adult CKD link was so apparent, that focusing on prevention of childhood obesity was likely to have a “larger effect than any treatment for CKD known to date.”

“We estimated that 36 percent of CKD cases at age 60-64 in the current U.S. population could be avoided if nobody became overweight until at least that age, assuming the same associations as in the analysis sample,” chief investigator Dorothea Nitsch, M.D., said in a statement. “To our knowledge we are the first to report how age of exposure to overweight across adulthood may affect kidney disease risk,” she added.

The authors acknowledged a number of limitations of the study including a low prevalence of reduced kidney function in the study cohort, as well as a “lack of study participants with reduced kidney function who never became overweight,” which forced them to combine never overweight and first overweight at 60-64 into a single category.

Finally, the “lack of repeated measures of kidney function meant that we were unable to ascertain CKD using the recommended definition of reduced kidney function for at least three months. This is likely to introduce nondifferential misclassification, again meaning that the true association is even stronger than described here,” they wrote.

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