“…The reviewed observational studies included cohort studies (13 papers), case–control studies (7 papers), and longitudinal design (3 papers). As far as the country of origin of the studies was concerned, four were performed in Italy [ 26 – 29 ], three in Japan [ 30 – 32 ], three in China [ 6 , 33 , 34 ], three in Australia [ 18 , 35 , 36 ], two in the UK [ 17 , 37 ], two in Denmark [ 38 , 39 ], two in the USA [ 40 , 41 ], one in France [ 42 ], one in Taiwan [ 10 ], one in Sweden [ 16 ], and one in Canada [ 43 ]. The number of participants in the studies varied from 40 to 1,429,585.…”