Children’s and adolescents’ risk of blood pressure increases and hypertension rose as their body mass index increased, even over a short period of a few years, according to a recent study.

“Obesity, especially severe obesity, at a young age confers an increased risk of early onset of cardiometabolic diseases such as hypertension,” wrote Emily D. Parker, Ph.D., of the HealthPartners Institute for Education and Research in Minneapolis, and her associates online (Pediatrics. 2016 Feb 19. doi: 10.1542/peds.2015-1662 ). “The significant adverse effect of weight gain and obesity early in life, and over a short period of time, emphasizes the importance of developing early and effective clinical and public health strategies directed at the primary prevention of overweight and obesity.”

The researchers retrospectively analyzed the health care records of 100,606 children and adolescents, aged 3-17 years, who received care from HealthPartners Medical Group in Minnesota, Kaiser Permanente Colorado, or Kaiser Permanente Northern California. All the patients had not been hypertensive within the 6 months before baseline measurements and had at least three primary care visits with blood pressure measurements between January 2007 and December 2011.

At baseline, 16% of the patients were overweight, 2% were obese, and 4% were severely obese. The majority (92%) were below the 90th percentile for their systolic blood pressure at baseline, while 4% were prehypertensive and 4% were hypertensive (at or above 95th percentile). Over a median 3.1 years of follow-up per person, 0.3% of the patients became hypertensive, translating to an incidence rate of 0.15 new cases per year.

After accounting for demographics, baseline blood pressure percentiles, year, and site, both children (aged 3-11) and adolescents with obesity were about twice as likely as children and adolescents with low healthy weights to develop hypertension (hazard ratio, 2.02 and HR, 2.20, respectively). Children and adolescents with severe obesity had more than a four times greater risk of developing hypertension (HR, 4.42 and HR, 4.46, respectively), compared with those with a low healthy weight. These were significant differences. No association appeared between those with low-normal weights at baseline and either high-normal or overweight categories during follow-up.

Forty percent of the children and 24% of the adolescents dropped from severely obese to obese during follow-up, and 45% of the children and 55% of the adolescents who were obese at baseline remained so throughout follow-up. Among children overweight at baseline, 19% became obese, 0.7% became severely obese, and 44% became a healthy weight. Among initially overweight adolescents, 13% became obese, 0.1% became severely obese, and 34% became a healthy weight.

“There was a strong association between change in BMI [body mass index] category and change in blood pressure across BMI categories in both age groups and genders,” Dr. Parker and her associates wrote. “In girls and boys 3-11 years old, both systolic blood pressure and diastolic blood pressure percentiles increased significantly when BMI increased from normal to either overweight or obese and when it increased from overweight to obese.” Similar but greater changes were seen among the adolescents, particularly among girls aged 12-17 years.

Correspondingly, children and teens who dropped from a higher to a lower BMI category had statistically significant drops in both systolic and diastolic blood pressure.

Risk of hypertension tripled for those with obesity at baseline who remained obese through follow-up (HR, 3.71 for children; HR, 3.64 for teens).

The study was funded by the National Heart, Lung, and Blood Institute. Most of the investigators had no relevant financial disclosures. Dr. Joan C. Lo has received previous research funding from Sanofi unrelated to this study.