Association of plasma retinol levels with incident cancer risk in Chinese hypertensive adults: a nested case-control study

We aimed to investigate the association between plasma retinol and incident cancer among Chinese hypertensive adults. We conducted a nested case-control study, including 231 patients with incident cancer and 231 matched controls during a median 4 center dot 5-year follow-up of the China Stroke Primary Prevention Trial. There was a significant, inverse association between retinol levels and digestive system cancer (per 10 mu g/dl increases: OR 0 center dot 79; 95 % CI 0 center dot 69, 0 center dot 91). When compared with participants in the first quartile of retinol (< 52 center dot 3 mu g/dl), a significantly lower cancer risk was found in participants in quartile 2-4 ( >= 52 center dot 3 mu g/dl: OR 0 center dot 31; 95 % CI 0 center dot 13, 0 center dot 71). However, there was a U-shaped association between retinol levels and non-digestive system cancers where the risk of cancers decreased (although not significantly) with each increment of plasma retinol (per 10 mu g/dl increases: OR 0 center dot 89; 95 % CI 0 center dot 60, 1 center dot 31) in participants with retinol < 68 center dot 2 mu g/dl, and then increased significantly with retinol (per 10 mu g/dl increase: OR 1 center dot 65; 95 % CI 1 center dot 12, 2 center dot 44) in participants with retinol >= 68 center dot 2 mu g/dl. In conclusion, there was a significant inverse dose-response association between plasma retinol and the risk of digestive system cancers. However, a U-shaped association was observed between plasma retinol and the risk of non-digestive cancers (with a turning point approximately 68 center dot 2 mu g/dl).