“…Table displays the characteristics of the included studies. A total of 18 studies with 142 921 subjects (5123 cases) published from 1989 through 2018 were identified, of which 15 were case‐control studies (4573 cases), 1 was case‐cohort study (152 cases), 1 was cohort study (292 cases), and 1 was randomized controlled study (106 cases) . Six of these studies were conducted in China, 2 in Sweden, 2 in Iran, 1 in Italy, 1 in South Korea, 1 in Lithuania, 1 in Netherlands, 1 in Turkey, 1 in Uruguay, 1 in the United States, and 1 in Venezuela.…”