Summary odds ratio of melanoma for the highest compared with lowest intake of vitamin A.

OR, odds ratio; CI, confidence interval; N, number of studies; P, p-value for heterogeneity tests.OR：比值比（odds ratio）；CI：置信区间（confidence interval）；N：研究数量（number of studies）；P：异质性检验的p值（p-value for heterogeneity tests）。