The Academy

By Prachi Patel-Predd
Published: Wednesday, Jun 16, 2010
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Jonsson Comprehensive Cancer Center

University of California, Los Angeles

Study Examines Impact of Sedentary Work On Prostate Cancer Risk

According to a new study from the University of California, Los Angeles’s (UCLA’s) Jonsson Comprehensive Cancer Center, the health hazards of a desk job may go beyond loss of fitness and carpal-tunnel syndrome. Findings presented by the researchers, published in a recent issue of Cancer Causes Control, suggest that men with desk jobs may be more likely to develop prostate cancer than those who are physically active each day at work.

Investigators examined the medical and job histories of more than 2,100 men at a nuclear and rocket engine testing facility in California’s San Fernando Valley. According to the data compiled by the study team, men who got little exercise at work, such as managers, analysts, and engineers, were more likely to have prostate cancer than people like masons, welders, and janitors who engaged in active physical labor.

The study compared 362 men who were diagnosed with prostate cancer from January 1988 and December 1999 with 1,805 men of similar ages and backgrounds who were cancer free. All worked at Rocketdyne Propulsion & Power, which Boeing Co. sold to United Technologies Corp. in 2005 for $700 million. The facility, located north of Los Angeles, has been used to test rockets since 1948. Employees were exposed to radiation and other chemicals that may boost their risk of prostate cancer, the researchers said.

The case-control study nested within a larger cohort of more than 10,000 male subjects who worked at the nuclear and rocket-engine testing site from the 1950s to the early 1990s. The cases of prostate cancer were diagnosed between January 1988 and December 1999. Researchers obtained cancer incidence data for the workers from the California Cancer Registry and seven other cancer registries in neighboring states where workers may have moved after retirement.

Data from Rocketdyne company records was used to construct a job exposure matrix that ranked job descriptions by the amount of physical activity required and any harmful exposures the workers might have experienced.

Physical activity was separated into jobs with low, moderate and high amounts of exertion. Men with low-activity jobs were typically managers, supervisors, analysts, administrators, and senior engineers. Those with moderately active jobs included senior mechanics and technicians, inspectors, and engineers. Masons and bricklayers, metal fitters, welders, packers, painters, tool and die makers, truck drivers, lift operators, and janitors were considered highly active.

The study found that the men who developed prostate cancer were less likely to have held the more physically active jobs. In addition to the association made by researchers between prostate cancer risk and the performance of physically inactive work, study findings also indicated that men who got cancer had more contact with and exposure to chemicals such as hydrazine, benzene, trichloroethylene, and polycyclic aromatic hydrocarbons. They also were more often black and more likely to have a family history of the disease and get tested regularly.

The findings support previous studies, which have asserted that regular physical exertion is needed to keep prostate cancer at bay. It remains unclear as to exactly how exercise combats the disease, the most common cancer in men, though some experts hypothesize that activity influences hormone levels to reduce the risk.

“The message from this study for today is that if you’re more active, you may be able to prevent this cancer from happening,’’ said Beate Ritz, MD, PhD, senior author of the paper and an Associate Professor of Epidemiology at the UCLA School of Public Health. “If you have a desk job, do something physically active to counterbalance it,” advised Dr. Ritz.

According to researchers, a strength of the study was that personnel records, job description manuals, industrial hygiene reviews, and interviews with retired workers were employed to develop the job exposure matrix, avoiding problems with subject recall and interviewer bias. Researchers were also able to obtain cancer incidence data and did not have to rely on mortality data. Prostate cancer is largely non-fatal, so mortality rates would not have been good data to analyze, Dr. Ritz said.

The study was limited in that researchers were not able to account for other potential factors that might affect prostate cancer risk, such as recreational physical activity and diet, said Anusha Krishnadasan, PhD, epidemiologist at Olive View–UCLA Education and Research Institute and first author of the study.

“All we can say for sure is that aerospace workers that were highly active on a regular basis for many years while working at Rocketdyne were at a decreased risk of prostate cancer,” summed up Dr. Krishnadasan.

Harvard Medical School, Boston

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