Rising Pulse Rates Suggest Children Are Less fit

A new study reports a modest but significant increase in resting pulse rates among preteens in the United Kingdom, suggesting a decline in overall fitness levels.

Researchers at the Institute of Child Health (London, United Kingdom) conducted a study that included close to 23,000 children between the ages of 9 and 11 who were part of a 1970 British birth cohort, and who were enrolled in various studies and surveys between 1980 and 2008 that included serial resting pulse rate measurements. Overall, average pulse rates were higher among girls, at 82.2 beats per minute (BPM) than in boys (78.7 BPM). Pulse rates rose consistently over the 30-year study period for both sexes, increasing by 0.07 BPM per year among boys and 0.04 BPM per year among girls.

The researchers also measured mean body mass index (BMI) increase during the study period, which showed an increase from 16.9 kg/m2 among boys and 17.1 kg/m2 among girls in 1980 to 18.8 kg/m2 and 19.2 kg/m2, respectively, in 2002, and remained high until 2008. At the same time, the prevalence of overweight/obesity increased from 5.7% among boys and 9.7% among girls in 1980 to 21.9% and 30.4%, respectively, in 2002, and remained high thereafter. But the trends for BMI accounted for only 13.8% of increase in pulse rate for boys and 17.2% for girls. The study was published on November 13, 2013, in the journal Archives of Disease in Childhood.

“Although modest, it is important to monitor these trends, especially in boys, as they appear to have increased at a faster rate in recent years,” concluded lead author Leah Li, MSc, and colleagues. “For boys, there was an indication that the trend was steeper after the mid-1990s, compared to the period prior to 1994.”

“Increases in physical activity in children would have a beneficial effect on their physical fitness and cardiovascular health while reducing resting pulse rate,” added Ms. Li. “If an increase of 2 beats per minute in mean resting pulse rate in boys persists to the adult population, this could result in a 4% increase in coronary heart disease mortality among healthy men and a 2% increase in risk of developing diabetes among those over 65 years.”

In adults, resting pulse rate has been linked to hypertension, atherosclerosis, and cardiovascular risk. In children, studies suggest that resting pulse rate is positively associated with blood pressure and adiposity. Resting pulse rate is also a recognized marker of physical fitness in both adults and children.

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Institute of Child Health