“…Only two studies fully documented three traditional cardiovascular risk factors (30,31), while the majority of studies only contained one or two cardiovascular risk factors. Furthermore, the included studies were conducted in many countries, including China (11,33,34), Canada (13,14,29), Sweden (15,16,27), United States (US) (17,28), United Kingdom (UK) (12,30), Italy (31), and Australia (32). Besides, the control group was matched according to age and gender with the case group in each study.…”