Cycling for health study

JOURNAL OF MEN’S HEALTH
Volume 11, Number 2, 2014 / (c) Mary Ann Liebert, Inc. / DOI: 10.1089/jomh.2014.0012
Milo Hollingworth, BSc, MBBS; Alice Harper, MA, MSc, MBBS; and Mark Hamer, BSc, PhD

Background
Cycling is a popular sport among men. Despite its health benefits, fears have been raised regarding its effects on erectile dysfunction (ED), fertility, and on serum prostate-specific antigen levels. This study aimed to examine associations between regular cycling and urogenital abnormalities in men.

Methods
A cross-sectional population study of 5,282 male cyclists was conducted in 2012–2013 as part of the Cycling for Health UK study. The data were analyzed for risk of self-reported ED, physician-diagnosed infertility, and prostate cancer in relation to weekly cycling time, categorized as < 3.75, 3.75–5.75, 5.76–8.5, and > 8.5 hours/week.

Results
There was no association between cycling time and ED or infertility, disputing the existence of a simple causal relationship. However, a graded increase ( p-trend = 0.025) in the risk of prostate cancer in men aged over 50 years (odds ratios: 2.94, 2.89, and 6.14) was found in relation to cycling 3.75–5.75, 5.76–8.5, and > 8.5 hours/week, respectively, compared to cycling < 3.75 hours/week.

Conclusions
These null associations refute the existence of a simple causal relationship between cycling volume, ED, and infertility. The positive association between prostate cancer and increasing cycling time provides a novel perspective on the etiology of prostate cancer and warrants further investigation.

cycling-for-health-study_2014  (full report)

“However the findings of this study demonstrated a direct relationship between risk of prostate cancer and cycling volume in cyclists aged over 50 years. This association was statistically significant after controlling for key confounding variables, including age. In addition, there was no association between cycling volume and primary care contact, suggesting that these fndings are not simply because of increased health awareness. To the best of our knowledge, this is the first study to demonstrate an association between prostate cancer and cycling, so there are no studies hypothesizing a pathophysiological mechanism for such a link. Perineal trauma may represent the underlying pathophysiology. Testicular cancer has been linked to cycling because of repetitive trauma to scrotal contents. Indeed, prostatitis has been described in cyclists and a meta-analysis has demonstrated that a history of prostatitis is associated with an increased risk of prostate cancer.

“The prevalence of prostatitis among cyclists is difficult to ascertain owing to a lack of evidence. Nevertheless, the effects of repetitive trauma on the prostate and carcinogenesis may be interesting avenues of study that may complement these findings. However, further prospective evidence is required to confirm this link. Indeed, it may be that cycling increases rates of diagnosis rather than risk of developing pathology. PSA has been found to be elevated in long-distance cyclists aged over 50 years.

“In addition, urogenital complaints such as hematuria, known as ‘‘bikeseat hematuria,’’ perineal soft-tissue lesions, ED, and perineal sensory abnormalities that are associated with cycling may lead to increased rates of investigation and subsequent diagnosis of other underlying conditions. This is speculative, however, but the presence of a biological gradient, and a compelling strength of association between prostate cancer and high cycling volumes warrant further investigation.

“There was no biological gradient between cycling time and ED or infertility, which is at odds with previous suggestions of a causal relationship. The findings suggest a graded association between cycling and risk of prostate cancer, but whether this is a definitive association related to causation or diagnosis remains to be seen.”