Blood glucose variability impacts heart rate dynamics in older type 2 diabetic and coronary heart disease patients

Table 1 Comparison of the general information between the two groups

	Normoglycemia group (n = 68)	Abnormal blood sugar fluctuation group (n = 75)	χ2/t	P value
Age (years)	64.91 ± 5.68	65.63 ± 5.72	0.754	0.452
Gender			0.116	0.733
Male	40	42
Female	28	33
Body mass index (kg/m2)	24.01 ± 1.39	23.55 ± 1.42	1.954	0.053
Course of diabetes mellitus (years)	5.27 ± 2.38	5.90 ± 2.29	1.610	0.110
Smoking history	25	27	0.009	0.924
Drinking history	10	11	0.007	0.995
Hypertension	37	40	0.017	0.897

Table 2 Comparison of blood glucose and glycosylated hemoglobin between two groups

Group	Number of cases	Fasting blood glucose (mmol/L)	HbA1c (%)
Normoglycemia group	68	9.55 ± 1.26	9.75 ± 2.77
Abnormal blood sugar fluctuation group	75	9.92 ± 1.61	10.09 ± 1.26
t value		1.541	0.942
P value		0.126	0.348

HbA1c: Glycosylated hemoglobin.

Table 3 Comparison of blood glucose fluctuation parameters between the two groups (mol/L)

Group	Number of cases	MAGE	MODD	LAGE	MPPGE
Normoglycemia group	68	3.07 ± 0.51	1.48 ± 0.33	5.71 ± 0.77	2.69 ± 0.85
Abnormal blood sugar fluctuation group	75	5.28 ± 1.24	2.45 ± 0.76	6.54 ± 1.24	3.97 ± 1.24
t value		4.685	4.235	4.514	4.387
P value		0.041	0.047	0.044	0.046

MAGE: Mean amplitude of glycemic excursions; MODD: Mean of daily differences; LAGE: Largest amplitude of glycemic excursions; MPPGE: Mean postprandial glucose excursions.

Table 4 Comparison of heart rate variability time-domain indicators between the two groups

Group	Number of cases	SDNN (ms)	SDANN (ms)	SDNNindex (ms)	rMSSD (ms)	pNN50 (%)
Normoglycemia group	68	113.62 ± 24.83	101.47 ± 19.86	30.45 ± 10.64	24.15 ± 6.07	7.99 ± 4.06
Abnormal blood sugar fluctuation group	75	96.45 ± 15.87	85.74 ± 13.62	22.12 ± 6.40	17.42 ± 3.88	5.01 ± 2.25
t value		22.016	26.432	9.013	8.764	5.216
P value		0.000	0.000	0.000	0.000	0.035

SDNN: Standard deviation of normal-to-normal interval; SDANN: Standard deviation of the average normal-to-normal interval; SDNNindex: Standard deviation of normal-to-normal intervals over every 5-minute period; rMSSD: Root mean square of successive differences; pNN50: Percentage of normal-to-normal intervals differing by > 50 ms.

Table 5 Correlation analysis between blood glucose fluctuation parameters and heart rate variability time domain indicators

Heart rate variability time domain indicator	MAGE		MODD		LAGE		MPPGE
	r value	P value	r value	P value	r value	P value	r value	P value
SDNN	-0.231	0.033	-0.198	0.042	-0.224	0.035	-0.291	0.000
SDANN	-0.218	0.036	-0.196	0.044	-0.269	0.024	-0.295	0.000
SDNNindex	-0.259	0.029	-0.195	0.045	-0.302	0.000	-0.289	0.000
rMSSD	-0.263	0.026	-0.206	0.040	-0.189	0.047	-0.214	0.036
pNN50	-0.201	0.039	-0.213	0.037	-0.254	0.021	-0.239	0.034

MAGE: Mean amplitude of glycemic excursions; MODD: Mean of daily differences; LAGE: Largest amplitude of glycemic excursions; MPPGE: Mean postprandial glucose excursions; SDNN: Standard deviation of normal-to-normal interval; SDANN: Standard deviation of the average normal-to-normal interval; SDNNindex: Standard deviation of normal-to-normal intervals over every 5-minute period; rMSSD: Root mean square of successive differences; pNN50: Percentage of normal-to-normal intervals differing by > 50 ms.

Table 6 Multivariate logistic regression analysis

Indexes	B	SE	Wald	Sig.	Odds ratio	95%CI
MAGE	1.847	0.794	5.452	0.029	0.164	0.031-0.737
MPPGE	1.129	0.331	9.164	0.015	2.845	1.544-5.952
SDNN	1.543	0.552	6.535	0.031	4.442	1.405-13.841

MAGE: Mean amplitude of glycemic excursions; MPPGE: Mean postprandial glucose excursions; SDNN: Standard deviation of normal-to-normal interval.