Table 1.
Sample characteristics and correlations with heart rate variability (N = 909)
| Correlations with ln-transformed HRV |
||||
|---|---|---|---|---|
| Variable | Mean (SD) or n (%) | SDRR | RMSSD | HF-HRV |
| Demographics | ||||
| Age, years | 57.39 (11.34) | −0.32*** | −0.21*** | −0.28*** |
| Male | 391 (43.01%) | 0.06† | −0.01 | −0.06† |
| White race (vs. Non-White) | 733 (80.64%) | −0.07* | −0.19*** | −0.22*** |
| Household income, median (Q1 - Q3) | $59,500 ($30,650 - $96,250) | 0.06† | −0.05 | −0.03 |
| Physical Health Covariates | ||||
| Body mass index, kg/m2 | 29.63 (6.40) | −0.07* | −0.00 | 0.01 |
| Number of comorbid conditions | 4.02 (2.91) | −0.22*** | −0.10** | −0.12*** |
| Medication use | ||||
| Cholesterol-lowering | 252 (27.72%) | −0.18*** | −0.12*** | −0.15*** |
| Corticosteroid | 37 (4.07%) | −0.07* | −0.06† | −0.05 |
| Blood pressure | 316 (34.76%) | −0.19*** | −0.03 | −0.05 |
| Health Behaviors from Clinic Visit | ||||
| Physical activity, 20+ min 3x/week | 702 (77.23%) | 0.03 | −0.02 | 0.007 |
| Cigarette smoking status | ||||
| Never smoked | 483 (53.14%) | 0.04 | −0.02 | 0.00 |
| Former smoker | 301 (33.11%) | −0.12*** | −0.08* | −0.10** |
| Current smoker | 125 (13.75%) | 0.11*** | 0.14*** | 0.14*** |
| Health Behaviors from Daily Interviews | ||||
| Daily physical activity, minutes | 41.32 (57.64) | 0.05 | 0.02 | 0.01 |
| Daily cigarettes smoked (n = 895) | 1.74 (5.19) | 0.06† | 0.09** | 0.10** |
| Daily Stress Processes a | ||||
| Daily negative affect (range: 0-4) | 0.21 (0.27) | −0.06† | −0.06† | −0.07* |
| Stressor frequency (% stressor days) | 42.48% (26.35%) | −0.01 | −0.04 | −0.04 |
| Stressor severity (n = 846)b | 1.74 (0.65) | −0.10** | −0.09* | −0.08* |
| Affective reactivity (n = 807)c | 0.17 (0.12) | −0.08* | −0.07* | −0.08* |
| Heart Rate Variability (ln-transformed) | ||||
| SD of RR intervals, ms | 3.46 (0.47) | --- | 0.83*** | 0.80*** |
| RMS successive RR differences, ms | 2.91 (0.63) | --- | --- | 0.96*** |
| High frequency (0.15-0.50 Hz), ms2 | 4.89 (1.29) | --- | --- | --- |
***
p ≤ 0.001,
**
p ≤ 0.01,
*
p ≤ 0.05,
†
p ≤ 0.10
a
Correlations between daily stress processes and HRV were partialed for age, income, and race, due to strong confounding relationships of demographics with stress and HRV.
b
Participants rated how stressful each event was, using a 0 (not at all) to 3 (very) scale. Seven percent of the sample (n = 63) did not experience a stressor during the 8 days of interviews.
c
Affective reactivity was defined as the change in negative affect on a stressor day, compared to a nonstressor day. Affective reactivity was not computed for 102 participants (63 did not have a stressor; 39 had stressors every day).