Elsevier

European Urology

Volume 60, Issue 5, November 2011, Pages 1029-1044
European Urology

Review – Prostate Cancer
Does Physical Activity Reduce the Risk of Prostate Cancer? A Systematic Review and Meta-analysis

https://doi.org/10.1016/j.eururo.2011.07.007Get rights and content

Abstract

Context

Numerous observational epidemiologic studies have evaluated the association between physical activity and prostate cancer (PCa); however, the existing results are inconsistent.

Objective

To determine the association between physical activity and risk of PCa.

Evidence acquisition

A systematic search was performed using the Medline, Embase, and Web of Science databases through 15 May 2011 to identify all English-language articles that examined the effect of physical activity on the risk of PCa. This meta-analysis was conducted according to the guidelines for the meta-analysis of observational studies in epidemiology.

Evidence synthesis

This meta-analysis consisted of 88 294 cases from 19 eligible cohort studies and 24 eligible case-control studies. When data from both types of studies were combined, total physical activity (TPA) was significantly associated with a decreased risk of PCa (pooled relative risk [RR]: 0.90; 95% confidence interval [CI], 0.84–0.95). The pooled RR for occupational physical activity (OPA) and recreational physical activity (RPA) were 0.81 (95% CI, 0.73–0.91) and 0.95 (95% CI, 0.89–1.00), respectively. Notably, for TPA, we observed a significant PCa risk reduction for individuals between 20 and 45 yr of age (RR: 0.93; 95% CI, 0.89–0.97) and between 45 and 65 yr of age (RR: 0.91; 95% CI, 0.86–0.97) who performed activities but not for individuals <20 yr of age or >65 yr of age.

Conclusions

There appears to be an inverse association between physical activity and PCa risk, albeit a small one. Given that increasing physical activity has numerous other health benefits, men should be encouraged to increase their physical activity in both occupational and recreational time to improve their overall health and potentially decrease their risk of PCa.

Introduction

Prostate cancer (PCa) is the second-most frequently diagnosed cancer and the sixth-leading cause of cancer death in males worldwide [1], [2]. However, the aetiology of PCa remains unclear [3]. Physical activity, a modifiable lifestyle factor, has been increasingly recognised to play an important role in the primary prevention of most adult cancers, including PCa [4], [5]. Although the precise biologic mechanisms that link physical activity and PCa risk remain unclear, it is plausible that physical activity may reduce the risk of PCa through the following pathways: It may influence the levels of some endogenous hormones associated with PCa risk, such as androgens [6], insulin [7], [8], and insulin-like growth factors [9], and regular activity may reduce levels of testosterone [10], serum insulin [11], and IGF-I [12], [13]. Physical activity also plays an important role in weight control and the prevention of obesity, which has been associated with the risk of aggressive PCa. In addition, physical activity can enhance immune function [14], [15], [16] and improve antioxidant defence mechanisms [17], [18], which could also reduce PCa risk [3].

The findings from numerous epidemiologic studies that have assessed the relationship between physical activity and PCa risk have been inconsistent. To date, no meta-analysis has been performed to evaluate the effects of physical activity on PCa risk, although several previous reviews [3], [5], [19], [20], [21], [22], [23], [24] have been assembled. However, these reviews did not consider the impact of study quality, study design, population sources, assessment methods for physical activity, length of the follow-up period in prospective studies, or an adjustment for confounding factors. In addition, several large cohort studies [25], [26], [27], [28], [29], [30], [31], [32], [33] and case-control studies [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46] from different geographic regions that were not included in the previous reviews have subsequently been published. Therefore, we conducted a systematic review and meta-analysis to precisely estimate the magnitude of the association between physical activity and PCa risk and to explore the underlying factors that may explain the heterogeneity using subgroup analyses.

Section snippets

Systematic search strategy

We systematically searched the Medline, Embase, and Web of Science databases through 15 May 2011 to identify all relevant English-language articles. A combination of Medical Subject Headings (MeSH) terms and corresponding free-text words was used (Appendix A). The reference sections of the retrieved articles were hand-searched for additional papers. This meta-analysis was conducted according to the meta-analysis of observational studies in epidemiology guidelines [47].

Study selection

We included studies that

Search results and reporting quality

We identified 43 articles that met the inclusion criteria (Fig. 1). The main characteristics of the 19 cohort studies and 24 case-control studies are summarised in Table 1, Table 2, respectively. The 19 prospective studies included 2 076 535 participants, with follow-up periods ranging from 2 to 26 yr and 74 942 PCa cases. The 24 case-control studies included 13 352 cases and 33 957 controls.

The methodologic quality scores were significantly higher for cohort studies than for case-control

Conclusions

Our findings indicate that OPA is associated with a small but significant PCa risk reduction. Long-term, regular RPA may also play a role in the primary prevention of PCa. Given that increasing physical activity has numerous other health benefits, men should be encouraged to increase their physical activity in both occupational and recreational time to improve their overall health and potentially decrease their risk of PCa.

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