A new large study reported in the American Journal of Hypertension shows a strong link between body mass index in teenagers and blood pressure. The researchers say the findings highlight the worrying implications of the rapidly growing global problem of teen obesity.
Teen obesity is a rising problem in many parts of the world. In the US, 17% of youngsters are obese.
There is a lot of evidence linking obesity to higher blood pressure.
However, much of the evidence comes from small studies that have yielded mixed results for younger age groups.
For their study, Dr. Yaron Arbel, of the Department of Cardiology at Tel Aviv Medical Center in Israel, and colleagues analyzed trends in teen obesity from 1998 to 2011 and examined the link between blood pressure and BMI in healthy youngsters.
The analysis took in data on 715,000 young people aged 16-20 years, 59% of them male, who underwent medical exams between 1998 and 2011 and were found fit for combat duties in the Israeli Defense Force.
The researchers found a statistically significant link between BMI and blood pressure, both of which rose significantly every year over the period of the study.
Body mass index or BMI is a measure of obesity that is equal to the height of the person in centimeters divided by the square of the weight in kilograms. BMI numbers for adults and teenagers are interpreted differently.
In this study of teenagers, the researchers defined overweight as having a BMI in excess of 25 kg/m2.
Blood pressure measurements comprise two figures: the higher figure is the systolic blood pressure or SBP – when the heart is pushing – and the lower figure is the diastolic blood pressure or DBP – when the heart is relaxing.
The study results show that in 1998, there were 13.2% overweight teenagers in the cohort. By 2011, this proportion had risen to 21%.
Over the same period, the percentage of adolescents with high blood pressure – measured as systolic blood pressure or SBP – rose from 7-28% in males and 2-12% in females.
The results show a much stronger tie between BMI and blood pressure in females than in males. The researchers did not study the reason for this but suggest it might be due to hormonal factors.
Dr. Arbel says the findings highlight the need to tackle childhood obesity. He says obese children are more likely to become obese adults, and “are consequently more at risk for adult health problems such as heart disease, type 2 diabetes, stroke, numerous types of cancer and osteoarthritis.”
He also notes that an important finding in their study is that “BMI was positively associated with SBP and DBP in both the normal weight and overweight groups,” and that:
“This highlights the importance of BMI as a marker for cardiovascular health in all body types.”
Some researchers say BMI is an inaccurate and misleading measure of fat content in the body. For example, in 2013, Medical News Today reported on a study from the University of Pennsylvania that discusses the challenges of using BMI when studying the mortality risks and health of obese people.