Obesity, High BMI Raise Hypertension Risk in Kids, Teenagers

Troy Brown, RN

February 25, 2016

Children and adolescents who become or remain obese are more than three times as likely to develop hypertension in a 3-year follow-up period compared with those who maintain a normal weight, according to a retrospective cohort study of more than 100,000 children and adolescents.

"Clinicians should recognize the relationship between [body mass index (BMI)] and [blood pressure (BP)]," lead author Emily D. Parker, PhD, MPH, from HealthPartners Institute for Education and Research, HealthPartners, Minneapolis, Minnesota, told Medscape Medical News. "The risk of hypertension was most concerning for those who maintained or increased to obesity or severe obesity. However, even among obese and severe[ly] obese children and adolescents, modest reductions in BP were seen with shifts to a lower BMI category (for example, from obese to overweight)."

"These findings underscore the importance of developing and implementing effective strategies to prevent excess weight gain in pediatric populations," Dr Parker said.

Dr Parker and colleagues report their findings in an article published online February 19 in Pediatrics.

The researchers analyzed data from the electronic health records of 101,606 children and adolescents aged from 3 to 17 years and without hypertension from three health systems in the United States. The children were seen between January 1, 2007 and December 31, 2011, and followed for a median of 3.1 years. The researchers computed BMI and BP percentiles and estimated the risk for incident hypertension for all the children and adolescents.

Baseline BMI and Risk for Incident Hypertension

After adjustment for sex, race, insurance type, baseline systolic BP (SBP) percentile, and other potential confounders, the researchers found no significant difference in the onset of hypertension between children of low and high normal weight at baseline and between children of low normal weight and overweight children.

Conversely, young children, aged 3 to 11 years, in the obese category at baseline were significantly more likely to develop hypertension (hazard ratio [HR], 2.02; 95% confidence interval [CI], 1.28 - 7.04), and the risks were similarly high for obese adolescents (HR, 2.20; 95% CI, 1.24 - 3.91). Severely obese children and adolescents were 4.42 (95% CI, 2.77 - 7.04) and 4.46 (95% CI, 2.39 - 8.31) times more likely to develop hypertension, respectively, compared with those of low healthy weight.

BMI Change and BP

Change in BMI category was strongly associated with change in BP across BMI categories in all children studied.

Boys and girls in the younger age group experienced significant increases in both SBP and diastolic blood pressure (DBP) when their BMI rose from normal to either overweight or obese, as well as when it increased from overweight to obese. Adolescents exhibited the same patterns, but with more marked changes. Girls aged 12 to 17 years had the greatest increases in SBP percentile.

SBP and DBP percentiles also increased significantly in those whose weight increased to severely obese.

In addition, "[children and adolescents who remained] overweight or obese had higher BP percentiles relative to healthy weight; even though there were decreases, on average, for maintaining overweight or obese, their absolute BP measures were still high relative to healthy weight," Dr Parker told Medscape Medical News.

"[O]bese children and adolescents who lost weight had modest decreases in SBP percentile," Dr Parker added.

BMI Change and Risk for Incident Hypertension

The authors found that not only baseline weight was important but also changes in weight. Among adolescents who increased from healthy weight to overweight, the risk of developing hypertension increased threefold (HR, 3.06; 95% CI, 1.42 - 6.59). Among children who went from overweight to obese, the risk increased fivefold (HR, 5.15; 95% CI, 2.24 - 11.86). The risk for incident hypertension was even increased for children and adolescents who changed from obese to overweight (HR, 1.79 [95% CI, 0.96 - 3.33], and HR, 1.46 [95% CI, 0.68 - 3.12], respectively).

In children and adolescents who stayed obese, the risk of developing hypertension more than tripled (HR, 3.71 [95% CI, 2.43 - 5.67], and HR, 3.64 [95% CI, 2.27 - 5.82], respectively).

The fact that hypertension developed during the 3-year follow-up period was not unexpected, Dr Parker noted. "We weren't terribly surprised because blood pressure is pretty variable: while measures tend to be correlated, there is still a lot of variability within a given individual," she said.

"It is important to emphasize that hypertension is very rare in children and adolescents. In our cohort of over 100,000 with normal blood pressure at baseline, only 343 developed hypertension (0.3%)," Dr Parker explained. "And we don't know what happens to their blood pressure after meeting the criteria for hypertension. Does it continue to increase? Does it remain in the hypertensive range? Or does it return to normal?"

The study was funded by the National Heart, Lung, and Blood Institute at the National Institutes of Health. The authors have disclosed no relevant financial relationships.

Pediatrics. Published online February 19, 2016. Abstract

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