Vagally mediated heart rate variability, stress, and perceived social support: a focus on sex differences

Figures & data

Table 1. Descriptive statistics for males and females.

Variable	Males (n = 82)	Females (n = 61)	t	χ2	p	φ	d	CI
Background information
Age (years)	20.17 (3.25)	19.62 (1.72)	1.20		0.23		0.20	[−0.13, 0.54]
Educational level	2.59 (0.74)	2.43 (0.72)		4.57	0.33	0.18		[−0.016, 0.33]
IPAQ	2.09 (0.65)	1.90 (0.54)		5.70	0.058	0.20		[−0.037, 0.35]
BMI (kg/m^2)	25.41 (4.75)	24.33 (5.08)	1.31		0.19		0.22	[−0.11, 0.56]
AUDIT	5.55 (3.85)	4.31 (4.17)	1.84		0.070		0.31	[−0.02, 0.65]
DAST	1.61 (1.02)	1.44 (1.07)	0.95		0.34		0.16	[−0.17, 0.50]
Questionnaire scores
MOS	28.90 (7.01)	31.77 (6.52)	−2.49		0.014*		−0.42	[−0.76, −0.09]
PSS	22.01 (5.41)	22.87 (5.93)	−0.90		0.37		−0.15	[−0.49, 0.18]
vmHRV	6.89 (1.23)	6.93 (1.30)	−0.21		0.84		−0.032	[−0.37, 0.30]
EDR (Hz)	0.23 (0.06)	0.23 (0.06)	−0.84		0.40		0.00	[−0.33, 0.33]
Mean HR	74.66 (10.17)	76.81 (12.51)	−1.13		0.40		−0.19	[−0.53, 0.14]

Note. Data are given as mean (SD). Degrees of freedom (df) were 145 for all variables, expect for IPAQ, where df was 2. IPAQ scores were re-categorized as low (1; ≤16th percentile), intermediate (2; 16th–84th percentile), and high (3; ≥84th percentile). CI: 95% confidence interval of d or φ, respectively. AUDIT: Alcohol use disorders identification test; BMI: Body mass index; DAST: Drug abuse screening test; IPAQ: International physical activity questionnaire; MOS: Medical outcomes study social support survey; PSS: Perceived stress scale; vmHRV: Vagally mediated heart rate variability, indexed by high frequency power (HF-HRV). HF-HRV values were log-transformed; EDR: Electrocardiogram (ECG) derived respiration; Mean HR: Mean heart rate (beats/min).

*= p < 0.05 **= p < 0.01.

Figure 1. Model for multiple moderation analysis, as A) designed by Hayes, and B) applied in the current study. Note. vmHRV: Vagally mediated heart rate variability, indexed by high frequency power (HF-HRV).

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In the model developed by Hayes, the antecedent variable is denoted as X, the outcome variable as Y, and moderators as W and Z, respectively. The applied model included vmHRV as X, perceived social support as Y, perceived stress as W, and sex as Z.

Table 2. Bivariate correlations among main study variables in the total sample and the two sexes, respectively.

Total sample
	MOS	PSS	Age	Educational level	BMI	IPAQ	AUDIT	DAST	EDR	Mean HR
vmHRV	0.076	−0.21*	−0.082	0.067	−0.074	0.17*	0.098	0.071	−0.16	−0.49**
MOS		0.0080	−0.17*	−0.15	−0.11	0.21*	−0.022	−0.015	0.079	−0.12
PSS			−0.060	0.000	0 .14	−0.16	0.060	0.038	0.098	0.12
Males
vmHRV	−0.12	−0.34**	−0.12	0.026	−0.0060	0.15	0.12	0.15	−0.032	−0.35**
MOS		0.067	−0.20	−0.22*	−0.025	0.30**	−0.014	0.014	0.029	−0.15
PSS			−0.059	−0.017	0.098	−0.20	−0.0040	0.021	0.18	0.12
Females
vmHRV	0.33**	−0.054	0.010	0.13	−0.15	0.22	0.083	−0.021	−0.31*	−0.65**
MOS		−0.11	−0.035	0.0030	−0.18	0.16	0.042	−0.016	0.11	−0.15
PSS			−0.047	0.041	0.21	−0.082	0.16	0.072	−0.0050	0.11

Note. AUDIT: Alcohol Use Disorders Identification Test; BMI: Body Mass Index (kg/m²); DAST: Druge Abuse Screening Test; EDR; Electrocardiogram (ECG) derived respiration; IPAQ: International Physical Activity Questionnaire; MOS: Medical Outcomes Study Social Support Survey; Mean HR: Mean heart rate; PSS: Perceived Stress Scale; vmHRV: Vagally mediated heart rate variability, indexed by high frequency power (HF-HRV). *= p < 0.05 **=p < 0.01.

Table 3. Moderation analyses of prediction of MOS.

Model summary
	R^2	F	df	Coeff.		SE	t	p	CI
vmHRV	0.44**	3.98	134	5.08		5.91	0.86	0.39	[−6.61, 16.77]
PSS				2.78		1.85	1.51	0.13	[−0.87, 6.43]
vmHRV*PSS				−0.36		0.27	−1.37	0.17	[−0.89, 0.16]
Sex				40.57		25.41	1.60	0.11	[−9.70, 90.83]
vmHRV*Sex				−4.77		3.57	−1.34	0.18	[−11.83, 2.29]
PSS*Sex				−2.35		1.11	−2.12	0.0357*	[−4.55, −0.16]
vmHRV*PSS*Sex				0.31		0.16	1.98	0.0496*	[0.0006, 0.63]
IPAQ				2.65		0.92	2.89	0.0045**	[0.84, 4.46]
Conditional effects of the focal predictor at the values of the moderators
	PSS	Percentile			Effect	SE	t	p	CI
Males (n = 82)	17	16th			−0.51	0.83	−0.61	0.54	[−2.16, 1.14]
	22	50th			−0.75	0.62	−1.21	0.23	[−1.98, 0.48]
	28	84th			−1.04	1.01	−1.03	0.30	[−3.03, 0.95]
Females (n = 61)	17	16th			0.066	0.82	0.081	0.94	[−1.55, 1.69]
	22	50th			1.40	0.64	2.17	0.031*	[0.13, 2.67]
	28	84th			3.00	0.88	3.41	<0.001**	[1.26, 4.73]

Note. Coeff.: Regression coefficient. CI: 95% confidence interval for the regression coefficient and effect, respectively. MOS: Medical outcomes study social support survey; vmHRV: Vagally mediated heart rate variability, indexed by high frequency power (HF-HRV); PSS: Perceived stress scale; vmHRV*Sex: Interaction term of vmHRV and sex; PSS*Sex: Interaction term of PSS and sex; vmHRV*PSS*Sex: Three-way interacion of vmHRV, PSS and sex; IPAQ: International physical activity questionnaire; Focal predictor: vmHRV. *= p < 0.05; **= p < 0.01.

Figure 2. Regression lines for males and females on the association between vmHRV and MOS scores in relation to varying PSS scores. Note. vmHRV: Vagally mediated heart rate variability, indexed by high frequency power (HF-HRV). MOS: Medical Outcomes Study Social Support Survey; PSS: Perceived Stress Scale. Low, intermediate and high PSS scores correspond to the 16th, 50th and 84th percentiles, respectively. *p ≤ 0.05 **p ≤ 0.01.

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Regression lines plotting the association between vmHRV and MOS scores in relation to low, intermediate and high PSS scores, for males and females. The association was significant only for females with intermediate and high PSS scores.

Data availability statement

The data that support the findings of this study are available on request from JK.