Associations between body composition and autonomic cardiorespiratory modulation in young adults.

Men showed greater respiratory variability and lower breathing rate than women.

• Sample included 90 university students aged 18-23 years (35 men, 55 women)
• Sex differences were observed in breathing rate variability (BRV) indices
• Men had lower absolute breathing rates compared to women
• Sex-stratified analyses were conducted throughout the study

In men, BMI, fat mass percentage, and visceral fat indices correlated negatively with parasympathetic modulation and complexity of cardiac and PRQ series.

• Negative correlations were found between adiposity indices (BMI, %FM, visceral fat) and parasympathetic HRV measures in men
• Adiposity indices also correlated positively with sympathetic modulation in men
• Both linear and nonlinear HRV indices were derived from 5-min R-R time series
• Pulse-respiratory quotient (PRQ) complexity was also negatively associated with higher adiposity in men
• These correlations were examined in sex-stratified analyses

Higher fat mass percentage was independently associated with lower vagally mediated HRV indices in men but not in women in multivariable regression models.

• Multivariable regression models were adjusted for age, breathing rate, and physical activity
• Physical activity was assessed with the IPAQ-short form and expressed as total METs/week
• %FM showed independent association with vagally mediated HRV in men after adjustment
• No significant independent association between %FM and vagal HRV was found in women
• This sex-specific finding persisted after controlling for confounders

Body composition was assessed using bioelectrical impedance providing fat mass percentage, muscle mass, and visceral fat indices alongside BMI.

• Bioelectrical impedance-based measures were obtained for all 90 participants
• Measures included fat mass percentage (%FM), muscle mass, and visceral fat indices
• BMI was also calculated as an additional body composition measure
• Participants were clinically healthy university students aged 18-23 years

The study incorporated complementary cardiorespiratory indices including breathing rate variability and pulse-respiratory quotient in addition to standard HRV.

• Linear and nonlinear HRV and BRV indices were derived from 5-min R-R and breath-to-breath time series
• Pulse-respiratory quotient (PRQ) time series were also analyzed
• Complexity measures of cardiac and PRQ series were included as nonlinear indices
• BRV and PRQ indices served as complementary measures to traditional HRV analysis

Higher adiposity was associated with reduced cardiorespiratory complexity particularly in young men.

• Diminished cardiorespiratory complexity was observed alongside reduced vagal HRV with higher adiposity
• This association was more pronounced in men than women
• Complexity of both cardiac and PRQ series was negatively associated with BMI, %FM, and visceral fat indices in men
• Participants were clinically healthy young adults, suggesting these autonomic changes occur even in the absence of overt disease