Abstract
Epidemiological studies have suggested inconclusive associations between 25-hydroxyvitamin D and total cancer incidence and mortality. The aim of this study was to quantitatively assess these associations by combining results from prospective cohort studies. A systematic literature search was implemented in PubMed and Scopus databases in April 2019. Comparing the highest with the lowest categories, the multivariate-adjusted relative risks (RRs) and the corresponding 95% confidence intervals (CIs) were pooled using a random-effects model. A trend estimation was performed using a two-stage, dose-response, meta-analysis method. Twenty-three independent prospective studies were included for data synthesis. Eight studies investigated the association between 25-hydroxyvitamin D and the risk of cancer incidence (7511 events and 70,018 participants), and the summary estimate showed that 25-hydroxyvitamin D is marginally associated with cancer risk (Summary RR = 0.86; 95% CI: 0.73, 1.02; I2 = 70.8%; p = 0.001). Sixteen studies investigated the association between 25-hydroxyvitamin D and the risk of cancer mortality (8729 events and 101,794 participants), and a higher 25-hydroxyvitamin D concentration was inversely associated with the risk of cancer mortality (Summary RR = 0.81; 95% CI: 0.71, 0.93; I2 = 48.8%, p = 0.012). Dose-response analysis indicated that the risk of cancer incidence was reduced by 7% (RRs = 0.93; 95% CI: 0.91, 0.96), and the risk of cancer mortality was reduced by 2% (RRs = 0.98; 95% CI: 0.97, 0.99), with each 20 nmol/L increment of 25-hydroxyvitamin D concentration. This meta-analysis provides evidence that a higher 25-hydroxyvitamin D concentration is associated with a lower cancer incidence and cancer mortality.
Highlights
Cancer is the leading cause of global morbidity and mortality, with approximately 18.1 million new cancer cases and 9.6 million cancer deaths in 2018 [1]
Dose-response analysis indicated that the risk of cancer incidence was reduced by 7% (RRs = 0.93; 95% corresponding intervals (CIs): 0.91, 0.96), and the risk of cancer mortality was reduced by 2% (RRs = 0.98; 95% CI: 0.97, 0.99), with each 20 nmol/L increment of 25-hydroxyvitamin D concentration
This meta-analysis provides evidence that a higher 25-hydroxyvitamin D concentration is associated with a lower cancer incidence and cancer mortality
Summary
Cancer is the leading cause of global morbidity and mortality, with approximately 18.1 million new cancer cases and 9.6 million cancer deaths in 2018 [1]. The number of people who died of cancer ranks second, second only to the number of deaths from cardiovascular and cerebrovascular diseases worldwide [2,3]. Great progress has been made in the prevention and treatment of certain cancers [4,5,6]. Despite these advances, the burden of cancer is increasing due to the increasing global population and ageing, as well as risk factors, such as smoking, obesity and unhealthy dietary patterns. It is necessary to identify many aspects of the beneficial factors for cancer prevention.
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