1. In a randomized control trial, caffeine administration was associated with greater cardiovascular effects in post-pubertal boys than girls.
2. Among postpubertal females, there was a significant interaction between the menstrual cycle phase and the effect of caffeine on heart rate and blood pressure.
Evidence Rating Level: 2 (Good)
Study Rundown: Caffeine consumption among children and adolescents is on the rise, with differences in the physiological response between boys and girls. In both adults and children, the acute cardiovascular effects of caffeine consumption include decreased heart rate and increased blood pressure. This study attempted to clarify the gender differences that exist in response to caffeine and the effects of puberty on this response. After abstaining from caffeine for 24 hours, participants were asked to drink a beverage containing 0, 1 mg/kg or 2 mg/kg caffeine, after which their blood pressure and heart rate were measured. Compared to postpubertal girls, boys experienced significantly greater changes in their systolic and diastolic blood pressure and heart rate. Postpubertal girls experienced significantly lower heart rate in the midluteal phase and significantly higher systolic blood pressure in the follicular phase of their menstrual cycles. There were no gender differences in the effect of caffeine in prepubertal boys and girls. Despite being a randomized controlled trial, this study is limited by the relatively homogenous race and socioeconomic status of the sample, as well as the study’s failure to verify caffeine abstinence outside of the study design. This study further elucidates differences in the physiological response to caffeine by gender and pubertal stage, paving the way for future research to uncover the underlying causes of these differences.
Study Author, Dr. Jennifer Temple, PhD, talks to 2 Minute Medicine: University at Buffalo, Associate Professor, Departments of Exercise and Nutrition Sciences and Community Health and Health Behavior, School of Public Health and Health Professions.
“Our study shows that, even at doses that might be considered low (around what you would find in a can or two of soda), caffeine can have an effect on heart rate and blood pressure in kids. Although our data do not suggest that this level of caffeine is particularly harmful, there is likely no benefit to giving kids caffeine and the potential negative effects on sleep should be considered when deciding what beverages to give to kids.”
In-Depth [randomized controlled trial]: This cross sectional, double-blind, placebo-controlled study included 96 participants ages 8 to 9 years (male n= 26, female n= 24) and 15 to 17 years (male n= 26, female n=20). Participants were mostly white (77%) and of upper middle class. Participants drank 300mL of juice or soda that contained 0, 1.0 mg/kg or 2.0 mg/kg of caffeine, after which their blood pressure and heart rate were measured every 10 minutes for 1 hour. Saliva samples were used to measure steroid hormone levels. Both the 1.0 mg/kg and 2.0 mg/kg doses of caffeine significantly reduced heart rate (z = -2.1, P = .04 and z = -2.7, P = .007, respectively) and increased systolic blood pressure compared to placebo (z = 2.1, P = .009 and P < 0.0001, respectively), overall. There was no significant gender difference in the effects of caffeine in prepubertal participants. However, there was a significant gender difference in heart rate (z = 1.98, P = .049) and blood pressure (z = 2.2, P = .03) among postpubertal participants. In postpubertal girls, there was a significant interaction between caffeine dose and menstrual phase on heart rate (P = .02) and blood pressure (P = .05 for diastolic, P = .002 for systolic). Heart rate was lowered more in the midluteal phase and blood pressure was increased more in the follicular phase.
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