Table 1 Characteristics of the included studies
|  |  |  | Age (yr), mean ± SD | Sex (M/F) | Duration (mo) | Study design | Reference | ||
|---|---|---|---|---|---|---|---|---|---|
Author | Year of publication | Total N | Tea | Control | Tea | Control | Â | Â | Â |
Iwata et al. | 1997 | 297 | 30 ± NA | 24 ± NA | NA | NA | 5 | Prospective cohort | [17] |
Yamada et al. | 2006 | 124 | 83 ± 8 | 83 ± 8 | 24/52 | 16/32 | 3 | Prospective cohort | [18] |
Yamada et al. | 2007 | 404 | 40 ± 11 | 40 ± 12 | 36/164 | 52/152 | 3 | Randomized controlled | [19] |
Toyoizumi et al. | 2013 | 308 | 16 ± 1 | 16 ± 1 | 98/57 | 86/67 | 3 | Randomized controlled | [21] |
Ide et al. | 2014 | 757 | 16 ± 1* | 16 ± 1* | 224/160* | 199/164* | 3 | Randomized controlled | [22] |