Association between folate level and cervical intraepithelial neoplasia risk: a systematic review and meta-analysis

There were several studies about the association between folate level and the risk of cervical intraepithelial neoplasia (CIN). This meta-analysis was conducted to evaluate whether folate deficiency is related to a high risk of CIN and cervical cancer. Odds ratios (ORs)/relative risks and 95% confidence intervals (CIs) were summarized regarding the association between folate level and risk of CIN or cervical cancer. The meta-analysis indicated that higher serum folate levels (the second, third, and fourth quartiles of serum folate) were associated with a lower risk of CIN, as demonstrated by a random-effects model (OR = 0.42, 95% CI: 0.28-0.62). Conversely, no significant association was found between erythrocyte folate levels and the risk of CIN, as indicated by a random-effects model (OR = 0.69, 95% CI: 0.43-1.12). In addition, random-effects models demonstrated that higher serum folate levels (the second, third, and fourth quartiles of serum folate) were associated with lower risks of CIN grade 1 and CIN grades 2 or 3, compared with the lowest quartile of serum folate (CIN grade 1: OR = 0.52, 95% CI: 0.29-0.93; CIN grades 2 or 3: OR = 0.33, 95% CI: 0.19-0.58). Higher serum folate levels (the second, third, and fourth quartiles of serum folate) were associated with a lower risk of cervical cancer, compared with the lowest quartile of serum folate (OR = 0.53, 95% CI: 0.36-0.79). Serum low folate levels could increase the risk of CIN and cervical cancer, while erythrocyte folate concentration was not associated with the risk of CIN.