Table 2.

The association between smoking status and HbA1c reduction was estimated by generalised estimating equations after propensity score matching.

Model 1: dichotomous smoking status			Model 2: four groups of smoking status
Variables	β (95% CI)	p-value	Variables	β (95% CI)	p-value
Group:			Group:
Non-smokers	0		Smoking (−/−)	0
Smokers	−0.11 (−0.37, 0.16)	.44	Smoking (−/+)	−0.10 (−0.68, 0.47)	.72
			Smoking (+/−)	−0.15 (−0.60, 0.31)	.52
			Smoking (+/+)	−0.11 (−0.40, 0.18)	.45
Time: Baseline	0		Time: Baseline	0
3 months	−2.60 (−2.81, −2.40)	<.001	3 months	−2.62 (−2.85, −2.40)	<.001
6 months	−2.73 (−2.94, −2.52)	<.001	6 months	−2.74 (−2.96, −2.51)	<.001
9 months	−2.63 (−2.84, −2.42)	<.001	9 months	−2.64 (−2.87, −2.42)	<.001
12 months	−2.68 (−2.88, −2.47)	<.001	12 months	−2.70 (−2.92, −2.47)	<.001
Interaction of smoking group and time			Interaction of smoking group and time
Baseline	0		Smoking (−/+): Baseline 0
3 months	0.33 (0.05, 0.62)	.02	3 months	0.12 (−0.46, 0.69)	.68
6 months	0.31 (0.02, 0.59)	.04	6 months	0.07 (−0.54, 0.69)	.81
9 months	0.25 (−0.04, 0.54)	.09	9 months	0.07 (−0.57, 0.71)	.84
12 months	0.30 (0.01, 0.59)	.04	12 months	0.18 (−0.44, 0.79)	.58
			Smoking (+/−): Baseline 0
			3 months	0.62 (0.12, 1.12)	.02
			6 months	0.58 (0.06, 1.10)	.03
			9 months	0.47 (−0.04, 0.99)	.07
			12 months	0.48 (−0.02, 0.98)	.06
			Smoking (+/+): Baseline 0
			3 months	0.29 (−0.03, 0.60)	.08
			6 months	0.25 (−0.06, 0.57)	.12
			9 months	0.21 (−0.10, 0.52)	.19
			12 months	0.29 (−0.02, 0.60)	.07

Note. The difference in HbA1c reduction between smokers and non-smokers was estimated by the regression coefficient (β) and 95% confidence interval (95% CI) of smoking status-by-time interaction at each time point. The models were established using the backward elimination method to select control variables, including a family history of diabetes, alcohol drinking, knowledge regarding glycemic control, medication adherence, anti-hypertensive agents, blood pressure, total cholesterol, estimated glomerular filtration rate, and body weight change.

Abbreviation: HbA1c: haemoglobin A1c.