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Physical Activity's Impact on Lung Cancer Risk in Male Smokers: A Longitudinal Study

This longitudinal study investigates the relationship between physical activity—both occupational and leisure time—and lung cancer risk among 27,087 Finnish male smokers aged 50-69 over a decade. Conducted by researchers from the National Cancer Institute and other institutions, it examines how variables such as age and smoking history influence this association. Although no inverse relationship was found between physical activity and lung cancer risk in long-term smokers, findings suggest a potential protective effect of leisure-time activity among younger men. The study highlights important considerations for assessing lung cancer risk factors.

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Physical Activity's Impact on Lung Cancer Risk in Male Smokers: A Longitudinal Study

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  1. Descriptive-longitudinal Study Colleen So Aaron Bryks Maile Capistrano Crystal Fong

  2. Physical Activity and Lung Cancer Risk in Male Smokers

  3. Authors & Affiliations • Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA • Lisa H. Colbert, Joseph A. Tangrea, Philip R. Taylor • Department of Nutrition, Pennsylvania State University, University Park, PA, USA • Terryl J. Hartman • Department of Epidemiology and Health Promotion, National Public Health Institute, Helsinki, Finland • Pirjo Pietinen, Jarmo Virtamo • Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA • Demetrius Albanes

  4. Grant Sponsor • National Cancer Institute, USA

  5. Purpose • Was to examine the association between physical activity (occupational and leisure-time) and lung cancer risk in a large group (27,087) of Finnish white male smokers, ages 50-69 over a period of 10 years.

  6. Type of Research • Prospective study • extrapolates to unknown outcomes • slow process • Longitudinal • assesses changes in behavior in one group of subjects at more than one point in time • e.g. over 10 year period • subjects act as their own controls • intra-individual variability is minimized

  7. Type of Research • Descriptive • reveals current patterns associated with a phenomenon (e.g. lung cancer) and how they relate to other factors • gives researchers something to build on for future research • does not include treatment or control group • does not attempt to determine causal relationships

  8. Research Methods • Study population: white male smokers enrolled in the Alpha-Tocopherol Beta-Carotene Cancer Prevention (ATBC) study • living in the southwestern Finland area • all subjects volunteered • smoked 5 or more cigarettes per day • between ages 50-69 • subjects recruited from 1985-1988

  9. Research Methods • Cases of lung cancer were identified through the Finnish Cancer registry • Examined the associations between occupational and leisure time physical activities and lung cancer • age • smoking characteristics: years of smoking, number of cigarettes smoked daily

  10. Research Methods • Collected baseline data • general medical history questionnaire • blood sample • Other question included in the questionnaire: • working environment -risk factor to lung cancer

  11. Research Methods • Crudely classified them as occupationally exposed: • asbestos • other causes of lung cancer (e.g. mining and quarrying) • Completed a self-administered food-use questionnaire • report usual frequency of consumption and portion size of more than 276 food items, mixed dishes and beverages during previous 12 months

  12. Research Methods • Two questions to assess usual occupational and leisure-time physical activity • 1st Question: Describe your activity during work in the past year as:

  13. Research Methods • 2nd Question: Describe your usual leisure-time activity in the past year as:

  14. Research Method • Sedentary men used as the reference group • Non-workers kept as a separate occupational activity category • includes retirees • Regular and heavy leisure-time physical activity combined to create an “active” leisure group

  15. Research Methods • Cox proportional hazards models were used to estimate the relative risk (RR) and 95% confidence intervals (CI) of lung cancer associated with level of physical activity • All models were run excluding the first 2 years of follow-up • no significant changes in any of the estimates

  16. Research Methods • Validity of the proportional hazards assumption was checked by examining the cross-product terms of follow-up time and the covariates of interest • no departures from this assumption for any covariate in the final models

  17. Main Findings • No inverse association between occupational and/ or leisure-time physical activity and risk of lung cancer in long-term cigarette smokers • may be due to length of time smoking • any beneficial effect of occupational activity may be outweighed by the related increase in risk due to exposure to asbestos and other high-risk exposures

  18. Main Findings • Only age appeared to modify the relationship between leisure-time activity and lung cancer • among younger men, approximately 20-25% of active men at lower risk • may be a protective relationship for leisure physical activity among younger smokers • no risk reduction among older men • may be due to the accumulation of more carcinogenic insults • slight increase of physical activity may go unnoticed

  19. Main Findings • Neither age nor amount of smoking modified the occupational physical activity association

  20. Main Findings • Non-workers appear to be at increased risk of lung cancer • Non-workers tend to be: • older • smoked longer • less educated • eat fewer vegetables • exposed to higher levels of carcinogens (asbestos)

  21. Main Findings • Men in moderate and heavy occupational activity categories, like non-working men, at increased risk to lung cancer • less education, higher exposure to carcinogens (e.g. asbestos) • perhaps non-working category may largely consist of men retired from occupations requiring moderate to heavy physical activity

  22. Main Findings • Men who participated in physical activity during their leisure time: • smoke fewer cigarettes/day • inhale smoke less often • consume foods of greater dietary energy sources and vegetables

  23. Weaknesses of Research Study • Sample is not generalizable to the entire population • reliability • if we were to conduct a similar study in the future, would we end up with the same results? • Homogeneous population (target sample) • not representative of entire population • population differences are controlled • amount of tobacco exposure • white males between ages of 50-69 from southwestern Finland

  24. Weaknesses of Research Study • Subjects derived from a previous study • no link between study objectives • subjects volunteered (convenience sampling) • selection bias

  25. Weaknesses of Research Study • Threats to internal validity: • possible history threat • an uncontrolled event that influences the participant’s testing outcomes over the extended period of time • selection bias • volunteers (convenience sampling) • whoever was available from the ATBC study • mortality • potential for high drop-out rates • changing the characteristics and qualities of the original sample

  26. Weaknesses of Research Study • Threats to internal validity (cont.): • instrumentation • studied white, long-term male smokers • used only one question each to measure usual occupational and leisure-time physical activity in the past year • questions are insufficient • many things can happen over a year • limited assessment (not specific enough)

  27. Weaknesses of Research Study • Threats to external validity: • reactive arrangement • social desirability • questionnaire: participants answer how they think you want them to answer • Does not evaluate long-term effects of asbestos exposure • non-working category (I.e. retirees) • Does not specify how often testing occurs over 10 year period

  28. Strengths of Research Study • Attempted to control for the influences of education, food consumption (in particular vegetables), and asbestos and other high-risk carcinogens • may still be residual confounding effects from these and/or other factors in our risk estimates • Controlled the type of people who were at the extremes of the population

  29. Strengths of Research Study • Prospective nature

  30. Considerations for Future Research • Use a more diverse population • careful considerations of smoking status • smokers and/or non-smokers • wider range of ages • different ethnicities and gender • Question more extensively to determine the level of physical activity at different ages associated with lung cancer • frequency, duration, type, and intensity of exercise

  31. Research Questions • Prospective research addresses changes that occur over time • e.g. "violence in children and television" • Descriptive research (e.g. studying a different culture) does not have any treatments • observational • no manipulation • observes natural progression that occurs within an environment

  32. Reference Colbert, L.H., Hartman, T.J., Tangrea, J.A., Pietinen, P., Virtamo, J., Taylor P.R., & Albanes, D., (2002). Physical Activity and Lung Cancer Risk in Male Smokers. Int. J. Cancer, 98, 770-773.

  33. Questions?

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