Table 1.

Study characteristics of smokers and non-smokers

Study	Country	No of participant	Intervention/control		Age/sex		Included/excluded from meta-analysis Study design
			Smoker	Non-smoker	Smoker	Non-smoker
Reynolds et al. [42] T2DM	USA	414	66	348	18.6 39.4% M	15.6 35.6% M	Included Cross sectional study
Reynolds et al. [42]T1DM	USA	2327	203	2124	18.3 50.7% M	14.2 50.5% M	Included Cross sectional study
Hofer et al. [43] T1DM	Austria and Germany	27,561	4051	23,510	13.66 21.6% M	13.66 78.4% M	Included Cross sectional study
Thomas et al. [44] T2DM	China and Hong Kong	496	196	300	53.5 100% M	53 100% M	Included Cross sectional study
Schwab et al. [45] T1DM	Germany	92	19	73	15.9 100% F	11.7 100% F	Excluded (skewed data) Cross sectional study
Wakabayashi et al. [46] T1 and T2 DM	Japan	2563	1332	1231	52.15	54.7	Included Cross sectional study
Hanesn et al. [47] T1DM	Denmark	32	16	16	31 87.5% M	31 87.5% M	Included Cross sectional study
Nilsson et al. [48] T1DM	Sweden	11,513	1646	9867	41.3 47% M	40.8 55% M	Included Cross sectional study
Nilsson et al. [48] T2DM	Sweden	40,648	4512	36,136	61.1 61% M	68.4 53% M	Included Cross sectional study
Gerber et al. [49] T2DM	UK	763	603	160	35.1 71.3% M	36.1 52.1% M	Included Prospective cohort study
Ohkuma et al. [50] T2DM	Japan	1184	679	505	65.6	61.2	Included Cross sectional study