Prostate cancer is the most common cancer in men in the UK, with around 47,500 cases a year (Prostate Cancer UK). It is also the second most common cause of cancer death in males in the UK, causing more than 11,500 deaths each year. This presents an urgent need to understand the factors which increase the risk of fatal prostate cancer. Although age, family history and black ethnicity are known risk factors, these are not modifiable, making it difficult to advise men on how to reduce their likelihood of developing prostate cancer.
Some previous studies have suggested that adiposity (amount of body fat) is a risk factor for lethal prostate cancer, with central adiposity (fat around the belly and waist) being particularly important. However, the small number of prostate cancer deaths included in individual studies have made it hard to draw firm conclusions.
To investigate this further, researchers from Oxford Population Health’s Cancer Epidemiology Unit, CEU carried out the largest meta-analysis to date of all the evidence published so far. This brought together data from 19 studies and over 2.5 million men, as well as data from a new analysis of more than 200,000 men in the UK Biobank study. The results are published in BMC Medicine.
For all the studies included in this Cancer Research UK-funded review, the men were free from any type of cancer when recruited and were followed for a set number of years, with the number of deaths from prostate cancer recorded. Adiposity was measured at the start of each study, with four different measures used: Body Mass Index, BMI (available for 19,633 prostate cancer deaths), waist circumference (3,181 deaths), waist to hip ratio (1,639 deaths), and body fat percentage (670 deaths).
- Higher adiposity scores were linked to a greater risk of dying from prostate cancer.
- Every five-point increase in BMI was found to increase the risk of dying from prostate cancer by 10%.
- The increase in risk was similar for central adiposity. Each 0.05 increase in waist to hip ratio increased the risk of fatal prostate cancer by 6%, whilst every 10 cm (3.9 inch) increase in waist circumference increased the odds by 7%.
- The researchers estimated that if the average BMI of men aged between 55 – 64 years old in the UK was reduced to be within the ideal range (18.5 to 24.9), there would be around 1,300 fewer prostate cancer deaths a year.
More research is needed to determine if the association is biologically driven or due to differences in detection. While some biological mechanisms have been proposed they are not well-established yet, and it is also possible that the disease may be harder to detect in men with obesity, leading to it being diagnosed later when it is harder to treat. In either case, our latest results provide another reason for men to try to maintain a healthy weight - Dr Aurora Perez-Cornago, lead author of the study