Table 2.

Subgroup analysis of metabolic syndrome (MetS) for the highest vs. lowest dietary iron level category.

Stratification	Number of studies	Pooled RR	95% CI	P- value	Heterogeneity
All studies	7	1.27	1.12, 1.44	P < 0.001	P = 0.01; I2 = 44%
Study design
Cross-sectional	5	1.31	1.13, 1.52	P < 0.001	P = 0.12; I2 = 45%
Cohort	2	1.34	0.72, 2.47	P = 0.35	P = 0.10; I2 = 62%
Race
Asian	4	1.44	1.13, 1.83	P = 0.003	P = 0.10; I2 = 53%
American	3	1.04	0.81, 1.32	P = 0.77	P = 0.69; I2 = 0%
Diagnostic criteria of MetS
NCEP ATP III	4	1.59	1.30, 1.93	P < 0.001	P = 0.75; I2 = 0%
Other	3	1.08	0.91, 1.27	P = 0.37	P = 0.62; I2 = 0%
Sample size
<1,000	2	0.94	0.53, 1.66	P = 0.83	P = 0.43; I2 = 0%
>1,000	5	1.34	1.09, 1.65	P = 0.006	P = 0.06; I2 = 56%
Exposure assessment
FFQ	1	2.04	0.97, 4.29	/	/
24 h or 3 days recall	6	1.25	1.10, 1.42	P < 0.001	P = 0.10; I2 = 45%
Type of iron
Heme iron	5	0.98	0.79, 1.22	P = 0.88	P = 0.04; I2 = 61%
Non-heme iron	5	1.25	1.08, 1.46	P = 0.004	P = 0.18; I2 = 36%