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Descriptive-longitudinal Study

Descriptive-longitudinal Study. Colleen So Aaron Bryks Maile Capistrano Crystal Fong. Physical Activity and Lung Cancer Risk in Male Smokers. Authors & Affiliations. Center for Cancer Research, National Cancer Institute, Bethesda, MD, USA

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Descriptive-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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