Association between Serum Vitamin C and the Blood Pressure: A Systematic Review and Meta-Analysis of Observational Studies

Table 1

The characters and the quality assessment of included studies.

First author	Year	Study area	Sample size			Age	BP value	Study design	Outcome	Adjusted variable	Quality score
			Male	Female	Overall		(SBP/DBP)
Zhao	1990	China	NA	NA	416	40-59	NA	Cross-sectional	Correlation coefficient	/	5
Moran	1993	USA	60	108	168	19-70	/	Cross-sectional	Correlation coefficient	/	6
Tse	1994	UK	39	34	73	C: N:	C: /; N: /	Case-control	Regression coefficient	Age, sex, smoking	7
Wen	1996	Ireland	32	27	59	C: N:	NA	Case-control		/	7
Toohey	1996	USA	42	126	168	F: M:	F: /; M: /	Cross-sectional	Correlation coefficient	/	4
Ness	1996	UK	835	1025	1860	45-75	/	Cross-sectional	Correlation coefficient; Regression coefficient	Age, sex and BMI	4
Pierdomenico	1998	Italy	NA	NA	42	C: N:	C: /; N: /	Case-control		/	7
Sakai	1998	Japan	919	1266	2185	≥40	F: /; M: /	Cross-sectional	Correlation coefficient	Age, sex, BMI, smoking, physical activity	5
Bates	1998	UK	NA	NA	541	≥65	/	Cross-sectional	Regression correlation	/	4
Tang	1998	China	NA	NA	84	30-60	NA	Case-control	Correlation coefficient	/	6
Sherman	2000	USA	31	21	52	C: N:	NA	Case-control		/	8
Langlois	2001	Belgium	96	123	219		C: /; N: /	Case-control		/	7
Chen	2002	USA	NA	NA	15317	≥20	C: /; N: /	Cross-sectional	OR	Age, sex, race, education, alcohol, BMI	7
Chen	2004	China	28	72	100	19-40	NA	Cross-sectional	Correlation coefficient	/	4
Rodrigo	2007	Chile	66	/	66	35-60	C: /; N: /	Cross-sectional	Correlation coefficient	/	5
Kumar	2014	Malaysia	NA	NA	690	56-64	C: /; N: /	Case-control		/	8
Zhou	2014	China	28	72	100	19-40	NA	Cross-sectional	Correlation coefficient	/	5
Naregal	2017	India	NA	NA	60	60-80	C: /; N: /	Cross-sectional	Correlation coefficient	/	5

C: case, N: non-case, F: female, M: male, M: mean, SD: standard deviation, SE: standard error, OR: odds ratio.