Adiposity, muscle, and physical activity: predictors of perturbations in heart rate variability.

OBJECTIVES: This study examines cross-sectional associations of indices of adiposity, lean body mass, and physical activity, with heart rate variability (HRV), a marker for parasympathetic cardiac vagal control. METHODS: The study population consists of 360 officers from the Buffalo New York Police Department. Indices of adiposity include body mass index, waist circumference, and a fat-mass index taken from dual-energy X-ray absorptiometry (DEXA) measurements. Lean body mass indices were derived from DEXA measurements of trunk mass and extremity lean mass. Physical activity was measured using a 7-day self-report questionnaire. HRV was obtained from 5-min electrocardiogram measurements by means of parametric spectral analysis resulting in estimates for high-frequency (HF) and low-frequency (LF) HRV. RESULTS: Both HF and LF HRV were significantly associated with markers for adiposity, two components of lean mass and physical activity with all associations being in the expected direction except that for trunk lean mass. This unexpected result is explained by the possibility that trunk mass is a marker for visceral adiposity rather than lean mass. Body mass index did not explain any additional variance in HRV above and beyond waist circumference and the DEXA indices. CONCLUSIONS: Higher levels of physical activity, lower levels of markers for central adiposity and higher lean mass in the extremities predict higher levels of HRV in this population of police officers. This association between modifiable risk factors and markers for autonomic function suggest possible interventions that may improve health and performance.

Associations of serum C-reactive protein with fasting insulin, glucose, and glycosylated hemoglobin: the Third National Health and Nutrition Examination Survey, 1988-1994.

This study investigated the associations between serum C-reactive protein and fasting blood levels of insulin, glucose, and hemoglobin A1c (HbA1c). Data from the Third National Health and Nutrition Examination Survey (1998-1994) were used. Study subjects included 2,466 men and 2,876 women who were > or = 17 years and nondiabetics with an overnight fast for blood draw. C-reactive protein was categorized into low (<0.3 mg/dl), moderate (0.3-0.9 mg/dl), and high (> or = 1.0 mg/dl) levels. Mean levels of insulin, glucose, and HbA1c were compared across C-reactive protein levels after adjustment for age, ethnicity, education, poverty index, cigarette smoking, alcohol use, and leisure time physical activity. For men with low (n = 1,818), moderate (n = 493), and high (n = 155) C-reactive protein, the adjusted means of insulin were 9.4, 11.7, and 10.5 microunits/ml (p < 0.01); glucose, 99.8, 101.6, and 100.6 mg/dl (p > 0.05); and HbA1c, 5.4%, 5.5%, and 5.5% (p < 0.05). For women with low (n = 1,816), moderate (n = 776), and high (n = 282) C-reactive protein, the adjusted means of insulin were 8.7, 11.2, and 13.7 microunits/ml (p < 0.01); glucose, 95.3, 97.9, and 105.2 mg/dl (p < 0.01); and HbA1c, 5.3%, 5.4%, and 5.6% (p < 0.01). In conclusion, elevated C-reactive protein was associated with higher insulin and HbA1c among men and women and with higher glucose levels among women only. These results suggest a possible role of inflammation in insulin resistance and glucose intolerance.