Relation between hematocrit and the risk of human common cancers: results from the 1999-2020 observational survey and Mendelian randomization analysis

Previous studies underscore the significance of hematocrit (HCT) in different tumors. It is imperative to conduct further research to explore the relationship between HCT and tumors. This study employed retrospective analysis and Mendelian randomization analysis (MRA) using a sample size of 19,408,959 to explore the relationship between high HCT levels and the risk of the 15 most prevalent malignant tumors. Kaplan-Meier curves were adopted to investigate the relationship between HCT and prognosis of patients with prostate cancer (PCa). An elevated HCT level was identified as a protective factor for six cancers, including PCa (odds ratio [OR] &lt; 1.000, <i>p</i> &lt; 0.05), while it was a risk factor for cervical cancer, melanoma, and non-melanoma skin cancer (OR &gt; 1.000, <i>p</i> &lt; 0.05). A potential causal association was found between high HCT levels and a decreased risk of PCa (OR = 0.887, <i>p</i> &lt; 0.05) and breast cancer (BRCA) (OR = 0.893, <i>p</i> &lt; 0.05). Using the in-house cohort, HCT was identified as a protective factor for PCa (<i>p</i> &lt; 0.05). This study identified associations between HCT and nine tumors. HCT may serve as a protective factor for the prognosis of patients with PCa. This study aimed to understand how hematocrit (HCT), a measure of the proportion of red blood cells in the blood, is related to different types of cancer. Previous research has suggested that HCT may play different roles in various cancers, so this study further explored this potential connection. Using data from over 19 million people, the researchers looked at the relationship between high HCT levels and the risk of developing the 15 most common cancers. They also examined whether HCT levels were linked to the outcomes for specific cancers, using additional data from health surveys and an internal database. For prostate cancer, they analyzed how HCT levels affected patient survival over time. The results showed that higher HCT levels seemed to lower the risk for several cancers, including bone, colon, esophageal, prostate, kidney, and stomach cancers. However, higher HCT was associated with an increased risk for cervical cancer, melanoma, and non-melanoma skin cancer. The study also found that high HCT levels were linked to a reduced risk of prostate and breast cancer, suggesting a possible protective effect. For prostate cancer patients, higher HCT levels were also associated with better survival outcomes. In conclusion, this study found that HCT levels are connected to the risk of various cancers in different ways, and higher HCT may help protect against certain cancers, particularly prostate and breast cancer.