Correlation between key indicators of continuous glucose monitoring and the risk of diabetic foot

Table 1 Comparison of general clinical data between the non-diabetic foot and diabetic foot groups, n (%)

Variables	NDF (n = 294)	DF (n = 297)	P value
Age, years	60.00 (52.00-69.00)	64.00 (54.00-71.00)	0.045
Male	160 (54.42)	189 (63.64)	0.023
BMI, kg/m2	24.23 (22.50-26.54)	24.34 (22.22-26.25)	0.672
WHR	0.93 (0.89-0.96)	0.90 (0.90-1.00)	< 0.001
Diabetes duration, months	72.00 (12.00-144.00)	120.00 (60.00-216.00)	< 0.001
Family history of diabetes	111 (37.76)	124 (41.75)	0.321
Smoking (current)	107 (36.39)	82 (27.61)	0.022
Drinking (current)	98 (33.33)	67 (22.56)	0.004
Presence of hypertension	165 (56.12)	196 (65.99)	0.014
Amputation	0	10 (3.37)	< 0.001
Left lower limb ABI	1.03 (1.01-1.06)	1.08 (1.01-1.15)	< 0.001
Right lower limb ABI	1.06 (1.03-1.10)	1.08 (1.02-1.15)	0.026
Antidiabetic drugs
Non insulin	78 (26.53)	24 (8.08)	< 0.001
Insulin	49 (16.67)	133 (44.78)	< 0.001
Both	167 (56.80)	140 (47.14)	0.019
Diabetic complications
DPN	286 (97.28)	282 (94.95)	0.143
DPVD	230 (78.23)	245 (82.49)	0.192
DAN	49 (16.67)	88 (29.63)	< 0.001
DN	126 (42.86)	167 (56.23)	0.001
DR	143 (48.64)	119 (40.07)	0.036
Biochemical indexes
WBC, × 109/L	6.68 (5.58-7.96)	7.30 (6.05-9.00)	0.000
NE, × 109/L	4.13 (3.21-4.99)	4.60 (3.70-6.40)	0.000
Hb, g/L	144.00 (132.00-155.00)	134.00 (118.00-148.50)	0.000
TC, mmol/L	4.66 (3.73-5.44)	4.20 (3.40-4.90)	0.000
TG, mmol/L	1.72 (1.12-2.55)	1.40 (0.90-2.00)	0.000
H-DLC, mmol/L	0.99 (0.83-1.18)	1.00 (0.80-1.10)	0.366
L-DLC, mmol/L	2.58 (1.89-3.18)	2.40 (1.80-3.10)	0.085
ALB, g/L	39.20 (36.55-41.70)	36.30 (32.40-39.50)	0.000
AST, U/L	19.00 (15.00-23.00)	19.000 (15.00-25.00)	0.812
ALT, U/L	19.00 (14.00-27.00)	18.00 (13.00-26.00)	0.072
eGFR, mL/min/1.73 m2	83.66 (65.15-109.49)	79.14 (57.83-102.70)	0.086
FPG, mmol/L	7.44 (5.54-10.31)	7.70 (5.70-10.45)	0.342
HbA1c, %	8.80 (7.20-10.53)	9.50 (7.75-11.00)	0.002
Islet function
FINS, μIU/mL	9.60 (5.69-15.60)	10.55 (5.52-19.05)	0.350
C-P, ng/mL	1.87 (1.24-2.59)	1.59 (0.86-2.59)	0.045
HOMA-β	44.97 (24.39-97.91)	47.72 (22.38-125.24)	0.546
HOMA-IR	3.55 (1.74-6.01)	3.42 (2.10-7.11)	0.376

Bold values indicate P < 0.05. Data were expressed as medians (25^th-75^th percentiles) for skewed distribution variables. Categorical variables were expressed as frequency (percentage). NDF: Non-diabetic foot; DF: Diabetic foot; BMI: Body mass index; WHR: Waist-to-hip ratio; ABI: Ankle-brachial index; DPN: Diabetic peripheral neuropathy; DPVD: Diabetic peripheral vascular disease; DAN: Diabetic autonomic neuropathy; DN: Diabetic nephropathy; DR: Diabetes retinopathy; WBC: White blood cell; NE: Neutrophils; Hb: Hemoglobin; TC: Total cholesterol; TG: Triglyceride; HDL-C: High-density lipoprotein cholesterol; LDL-C: Low-density lipoprotein cholesterol; ALB: Albumin; AST: Aspartate aminotransferase; ALT: Alanine aminotransferase; eGFR: Estimated glomerular filtration rate; FPG: Fasting plasma glucose; HbA1c: Hemoglobin A1c; FINS: Fasting insulin; C-P: C-Peptide; HOMA-β: Homeostasis model assessment of β cell function; HOMA-IR: Homeostasis model assessment of insulin resistance.

Table 2 Comparison of continuous glucose monitoring-derived metrics between the non-diabetic foot and diabetic foot groups

Variables	NDF (n = 294)	DF (n = 297)	P value
CGM-derived metrics
MBG, mmol/L	8.23 (7.33-9.81)	9.20 (8.00-10.70)	< 0.001
SD, mmol/L	2.34 (1.80-2.92)	2.40 (1.80-3.25)	0.129
CV, %	26.80 (22.11-32.80)	26.32 (20.56-33.78)	0.496
LAGE	11.82 (8.98-14.71)	11.50 (8.80-15.25)	0.929
GRI	24.52 (10.21-42.77)	35.98 (18.87-59.29)	< 0.001
TIR, %	76.90 (58.00-88.73)	65.91 (43.68-81.95)	< 0.001
TAR, %	20.26 (9.37-41.59)	32.57 (16.26-55.43)	< 0.001
TAR level 1, %	17.03 (8.44-31.71)	25.35 (13.56-38.90)	< 0.001
TAR level 2, %	2.81 (0.00-8.60)	5.04 (0.00-14.97)	< 0.001
TBR, %	0.00 (0.00-1.24)	0.00 (0.00-0.69)	0.114
TBR level 1, %	0.00 (0.00-1.08)	0.00 (0.00-0.62)	0.197
TBR level 2, %	0.00 (0.00-0.00)	0.00 (0.00-0.00)	0.031
CGM-derived indicator achievement, n (%)
CV target	250 (85.03)	240 (80.81)	0.172
TIR target	180 (61.22)	128 (43.10)	< 0.001
TAR level 1 target	196 (66.67)	146 (49.16)	< 0.001
TAR level 2 target	182 (61.90)	148 (49.83)	0.003
TBR level 1 target	262 (89.12)	269 (90.57)	0.558
TBR level 2 target	279 (94.90)	284 (95.62)	0.678

Bold values indicate P < 0.05. Data were expressed as medians (25^th-75^th percentiles) for skewed distribution variables. Categorical variables were expressed as frequency (percentage). NDF: Non-diabetic foot; DF: Diabetic foot; CGM: Continuous glucose monitoring; MBG: Mean blood glucose; CV: Coefficient of variation; LAGE: Maximum glucose fluctuation range; GRI: Glycemia risk index; TIR: Time in range; TAR: Time above range; TBR: Time below range.

Table 3 Logistic regression analysis of the correlations between continuous glucose monitoring-derived metrics and the risk of diabetic foot

Variable	Multivariate logistic regression
	β	OR	95%CI	P value
MBG
Model 1	1.056	2.876	1.876-4.409	< 0.001
Model 2	0.948	2.582	1.642-4.058	< 0.001
Model 3	0.998	2.712	1.697-4.334	< 0.001
Model 4	0.654	1.923	1.103-3.353	0.021
Model 5	0.813	2.255	1.222-4.163	0.009
TIR
Model 1	-0.182	0.834	0.776-0.895	< 0.001
Model 2	-0.167	0.846	0.784-0.913	< 0.001
Model 3	-0.180	0.836	0.772-0.904	< 0.001
Model 4	-0.114	0.892	0.814-0.978	0.015
Model 5	-0.143	0.867	0.784-0.957	0.005
TAR level 1
Model 1	0.249	1.283	1.156-1.424	< 0.001
Model 2	0.230	1.258	1.126-1.406	< 0.001
Model 3	0.243	1.275	1.138-1.429	< 0.001
Model 4	0.173	1.189	1.044-1.353	0.009
Model 5	0.203	1.225	1.065-1.407	0.004
TAR level 2
Model 1	0.258	1.294	1.121-1.493	< 0.001
Model 2	0.236	1.266	1.088-1.473	0.002
Model 3	0.253	1.287	1.099-1.508	0.002
Model 4	0.104	1.109	0.930-1.324	0.250
Model 5	0.168	1.183	0.970-1.442	0.098
GRI
Model 1	0.141	1.151	1.084-1.223	< 0.001
Model 2	0.131	1.140	1.068-1.216	< 0.001
Model 3	0.141	1.151	1.077-1.231	< 0.001
Model 4	0.084	1.087	1.007-1.175	0.033
Model 5	0.109	1.115	1.024-1.213	0.012

Odds ratios represent per 5% increase in mean blood glucose, per 10% increase in time in range, time above range (TAR) level 1, TAR level 2, and per 10-unit increase in glycemia risk index. Model 1: Non-adjusted; Model 2: Adjusted for age, sex, body mass index, waist-to-hip ratio, diabetes duration, smoking, drinking; Model 3: Model 2+ presence of hypertension, diabetic autonomic neuropathy, diabetic nephropathy, diabetes retinopathy; Model 4: Model 3+ white blood cell, hemoglobin, triglyceride, total cholesterol, albumin, and hemoglobin A1c; Model 5: Model 4+ left lower limb ankle-brachial index (ABI), right lower limb ABI, and antidiabetic drugs. MBG: Mean blood glucose; GRI: Glycemia risk index; TAR: Time above range; TIR: Time in range.