Table 3.

Association Between Longitudinal Changes in Cardiorespiratory Fitness and Measures of Adiposity with Heart Rate Variability at Year 20, CARDIA

Independent variable		OR	95% CI	P value
Lower 25th percentile of SDNN (ms)
Graded exercise test duration (s)*	Model 1	1.550	1.130, 2.126	0.0065
	Model 2a: Model 1 + % increase in WC	1.504	1.086, 2.083	0.0140
	Model 2b: Model 1 + % increase in BMI	1.523	1.102, 2.104	0.0108
Waist circumference (cm)†	Model 1	1.193	0.952, 1.494	0.1247
	Model 2c: Model 1 + % decrease in GXT duration	1.104	0.873, 1.395	0.4087
BMI (kg/m2)†	Model 1	1.169	0.936, 1.460	0.1674
	Model 2c: Model 1 + % decrease in GXT duration	1.081	0.860, 1.359	0.5050
Lower 25th percentile of RMSSD (ms)
Graded exercise test duration (s)*	Model 1	1.938	1.387, 2.709	0.0001
	Model 2a: Model 1 + % increase in WC	1.733	1.228, 2.445	0.0017
	Model 2b: Model 1 + % increase in BMI	1.851	1.315, 2.605	0.0004
Waist circumference (cm)†	Model 1	1.554	1.230, 1.963	0.0002
	Model 2c: Model 1 + % decrease in GXT duration	1.401	1.099, 1.786	0.0065
BMI (kg/m2)†	Model 1	1.317	1.051, 1.651	0.0169
	Model 2c: Model 1 + % decrease in GXT duration	1.176	0.931, 1.484	0.1734

BMI, body mass index; CI, confidence interval; GXT, graded exercise test; OR, odds ratio; RMSSD, the square root of the mean value of the squares of differences between all successive RR intervals; SD, standard deviation; SDNN, standard deviation of all normal RR intervals; WC, waist circumference

Model 1: Adjusted for sex, race, study center and Year 20 covariates: age, educational level, diabetes, hypertension, smoking status, use of β-blockers and use of calcium channel blockers

^*Percent change in GXT duration: ≥10% longitudinal decrease vs. no change or longitudinal increase

^†Change in measures of adiposity: ≥10% longitudinal increase vs. no change or longitudinal decrease

Dependent variable: Lower 25^th percentile HRV vs. higher 75^th percentile HRV (referent)