Table 1.

summaries the characteristics and NOS score of the selected studies

Authors	Year	Race	Country	Sample size		Gender(M/F)		Age		Study design	Diabetes mellitus type	Measure tool	NOS
				Cases	Controls	Cases	Controls	Cases	Controls
Keoliean [30]	1992	Caucasians	America	14	14	Nm	Nm	33 ± 12	33 ± 10	CS	Type 1	Widefieldspecular microscope	6
Larsson [31]	1996	Caucasians	America	49	20	Nm	Nm	36 ± 12	36 ± 12	CS	Type 1	Broomall Pa	6
				60	20	Nm	Nm	60 ± 10	59 ± 12	CS	Type 2	Broomall Pa	6
Siribunkum [32]	2001	Asians	Thailand	60	60	20/10	20/10	60.0 ± 9.1	60.4 ± 11.7	CC	Type 1 and 2	EM-1020	5
Inoue [33]	2002	Asians	Japan	99	97	53/46	52/45	65.5 ± 7.5	67.6 ± 7.3	CS	Type 2	NONCON ROBO CA	6
Cho o[34]	2010	Asians	Malaysia	100	100	Nm	Nm	Nm	Nm	CC	Type 2	SP-3000P	7
Jr [35]	2010	Caucasians	Hungary	41	40	12/9	13/9	40.97 ± 15.46	40.45 ± 15.16	CS	Type 1	EM-1000	7
				59	60	10/20	15/15	64.36 ± 10.47	62.69 ± 13.38	CS	Type 2	EM-1000	7
Sudhir [36]	2012	Asians	India	1191	120	637/554	58/62	54.8 ± 9.5	51.9 ± 8.7	CS	Type 2	SP-8000	6
Paulsen [37]	2013	Caucasians	Denmark	107	128	51/56	49/79	72.1 ± 11.0	75.6 ± 8.9	CS	Type 2	SP-2000P	6
Urban [38]	2013	Caucasians	Poland	123	124	60/63	66/58	15.34 ± 3.06	14.58 ± 2.01	CS	Type 1	SP-2000P	6
Arici [39]	2014	Caucasians	Turkey	60	109	12/18	18/33	54.8 ± 9.6	53.3 ± 8.2	CS	Type 2	SP-3000P	6
Wichi [40]	2015	Asians	Thailand	171	156	41/49	34/56	58.49 ± 9.78	58.98 ± 13.12	CS	Type 1 and 2	CS 4	4
Galgauskas [41]	2015	Caucasians	Lithuania	123	120	31/31	32/33	45.5 ± 13.4	45.4 ± 19.5.	CS	Type 2	SP-9000	7
Wichai [42]	2016	Asians	Thailand	271	82	63/85	16/30	61.04 ± 9.51	57.93 ± 11.30	CS	Type 1 and 2	CS 4	5
Islam [43]	2017	Asians	Pakistan	149	149	89/60	77/72	54.13 ± 9.97	52.01 ± 12.10	CS	Type 1 and 2	SP-3000P	7
Amira [44]	2017	Caucasians	Saudi	57	45	27/30	22/23	57.08 ± 8.37	50.80 ± 8.39	CS	Type 2	EM-3000	5
Veysel [11]	2018	Caucasians	Turkey	153	146	76/77	71/75	54.9 ± 6.6	53.9 ± 7.3	CS	Type 2	SP-3000P	7

CS Cross-sectional, CC Case-control, NM Not Mention