Association of heart rate variability index with depressive symptoms and lung function in chronic obstructive pulmonary disease

Table 1 Socio-demographic and clinical characteristics of 120 patients with chronic obstructive pulmonary disease, mean ± SD

	Patient (n = 120)	Percentage (%)
BDI score		8.2 ± 6.5
Depression	43.00	35.80
Males	110	91.67
Age (years), median (P25-P75)	67.7 (61.2-73.8)
Married	96	80.00
Less than primary education	49	40.83
Low socioeconomic status (IV-V)	97	80.83
Current workers	19	15.83
Smoking status
Current smoker	39	32.50
Former smoker	80	66.67
Never smoked	1	0.83
MMRC dyspnea scale, median (P25-P75)	2 (2-3)
Hemoglobin, g/dL	14.5 ± 1.4
Albumin, g/dL	4.2 ± 0.5
Diffusing capacity for carbon monoxide	65.1 ± 18.3
PaO2 (mmHg)	73.5 ± 10.4
PaCO2 (mmHg)	52.6 ± 17.3

BDI: Beck depression inventory; MMRC: Modified medical research council; PaO₂: Partial pressure of oxygen in arterial blood; PaCO₂: Partial pressure of carbon dioxide in arterial blood.

Table 2 Comparison of depressive symptoms and pulmonary function indicators in each group, mean ± SD

Variable	Without depression (n = 77)	Depression (n = 43)	Control (n = 60)	P value
BDI score	5.7 ± 4.3	21.8 ± 5.9	2.6 ± 1.5	< 0.001
Lung function
FEV1 (L)	2.86 ± 0.67	2.06 ± 0.43	3.65 ± 0.78	< 0.001
FVC (L)	2.90 ± 0.72	1.43 ± 0.82	3.46 ± 0.57	< 0.001
FEV1/FVC	72.1 ± 6.03	58.2 ± 6.73	88.2 ± 8.76	< 0.001

BDI: Beck depression inventory; FEV1: First-second expiratory volume; FVC: Forced vital capacity.

Table 3 Comparison of relevant indexes of heart rate variability of subjects in each group, mean ± SD

Variable	Without depression (n = 77)	Depression (n = 43)	Control (n = 60)	P value
SDNN (ms)	108.32 ± 17.68	83.21 ± 14.26	148.27 ± 34.73	< 0.001
SDANN (ms)	101.17 ± 13.82	84.54 ± 11.24	136.38 ± 24.12	< 0.001
rMSSD (ms)	32.47 ± 10.23	23.62 ± 8.21	42.72 ± 11.24	< 0.001
PNN50 (%)	13.68 ± 4.91	7.41 ± 2.03	23.85 ± 7.43	< 0.001
HF (ms)	2689.21 ± 841.38	1037.64 ± 302.54	6983.62 ± 1096.37	< 0.001
LF (ms)	963.81 ± 164.82	547.92 ± 110.04	1182.73 ± 287.41	< 0.001

SDNN: Standard deviation of normal-to-normal intervals; SDANN: Standard deviation of the average of normal-to-normal intervals; rMSSD: Root mean square of successive differences of normal-to-normal intervals; PNN50: Percent of pairs of successive normal intervals that differ by more than 50 ms; HF: High frequency; LF: Low frequency.

Table 4 Correlation between heart rate variability, Beck Depression Inventory score and lung function in chronic obstructive pulmonary disease patients

HRV		SDNN (ms)	SDANN (ms)	rMSSD (ms)	PNN50 (%)	HF (ms)	LF (ms)
BDI	r value	-0.673	-0.712	-0.706	-0.731	-0.632	-0.613
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FVC	r value	0.743	0.772	0.692	0.713	0.791	0.732
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FEV1	r value	0.782	0.731	0.785	0.698	0.801	0.763
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001
FEV1/FVC	r value	0.719	0.692	0.783	0.772	0.795	0.697
	P value	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001	< 0.001

SDNN: Standard deviation of normal-to-normal intervals; SDANN: Standard deviation of the average of normal-to-normal intervals; rMSSD: Root mean square of successive differences of normal-to-normal intervals; PNN50: Percent of pairs of successive normal intervals that are differing by more than 50 ms; HF: High frequency; LF: Low frequency; HRV: Heart rate variability; FEV1: First-second expiratory volume; FVC: Forced vital capacity.