Multiple groups, Three of them were conducted in China, two in the U.S.A., one in Canada, one in Finland, and one in Korea. Six of them were cohort studies, and two were randomized controlled trials.
特征
Meta-analysis of Birmingham (2015a and b), Huguet 2016, Keskitalo 2009, Liu 2016, Wan 2015, Zhang 2006
生物地理组
Multiple groups, Three of them were conducted in China, two in the U.S.A., one in Canada, one in Finland, and one in Korea. Six of them were cohort studies, and two were randomized controlled trials.