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DanishCancerSoc291104Hardman

VIEWS: 1 PAGES: 28

									School of Sport & Exercise
                  Sciences




                             Physical activity, obesity and
                             cancer – a review of current
                                   knowledge and
                                  recommendations


                                    Adrianne E Hardman
                  Outline
•   Measuring exposure to physical activity
•   Colorectal cancer
•   Breast cancer
•   Other cancers
•   Recommendations
•   Summary
   Assessment of exposure
§ Sources – activities of daily living, occupation,
             recreation

§ Components – intensity, duration, frequency

§ Time periods in life – childhood, adolescence,
                       – lifetime, recent
§ Fitness – acquired through participation in
  high levels of vigorous activity
   Measures of physical activity
§ Intensity
  § Participation in activities known to incur a high rate
    of energy expenditure
  § METs – multiples of resting metabolic rate
  § Descriptors – ‘vigorous’, ‘hard enough cause sweating’


§ ‘Volume’ = intensity x duration x frequency
  § Energy expenditure in MJ (kcal) per week
  § MET-hours
                Examples
• 1000 kcal (4.2 MJ) per week
  - approximately 2.5 h of moderate intensity
    physical activity per week

• MET-h
  – Brisk walking (4.5 METs) daily for one hour
  is (4.5 x 1 x 7) = 31.5 MET-h per week
  – Doubles tennis (6 METs) for 1.5 hours,
  three times per week is (6 x 1.5 x 3) = 27
  MET-h per week
                  Outline
•   Measuring exposure to physical activity
•   Colorectal cancer
•   Breast cancer
•   Other cancers
•   Recommendations
•   Summary
  Physical activity and risk of
 colon cancer in Harvard alumni

                                    High; >2500 kcal/wk
                                    Mod: 1000-2500 kcal/wk




Lee I-M et al J Natl Cancer Inst 1991;83:1324
Relative risk of colon cancer by
 leisure-time physical activity




                                      P trend = 0.03




Martínez et al J Natl Cancer Inst 1997;89:948
Energy balance, physical activity
 and risk of colon cancer in men




  Slattery et al Cancer Res 1997;57:75
Risk of colon cancer in people with
  high energy intake & high BMI

                    Odds ratio          95% CI

Low physical            3.35           2.09 – 5.35
activity

High physical           1.28           0.81 – 2.03
activity

Slattery et al Cancer Res 1997;57:75
     Exercise and colon cancer:
        ‘convincing’ evidence
• Consistent 30-40% lower risk, RR 0.6-0.7
• Independent of confounding factors,
  including BMI
• Findings replicated in different
  populations
• Dose-response evident: 30-60 min/day of
  moderate to vigorous activity is optimal
• No effect on risk of rectal cancer
                  Outline
•   Measuring exposure to physical activity
•   Colorectal cancer
•   Breast cancer
•   Other cancers
•   Recommendations
•   Summary
   Physical activity & breast
cancer risk in Norwegian women




Thune et al N Engl J Med 1997;336:1269-75
  Physical activity and breast
  cancer: case-control study




Friedenreich et al Am J Epidemiol 2001;154:336-47
        US Women’s Health
      Initiative Cohort Study




McTiernan A et al JAMA 2003:290:1331-6
     Breast cancer risk by
     activity level and BMI




McTiernan A et al JAMA 2003;290:1331-6
   Physical activity and breast
  cancer – ‘convincing’ evidence
• 55 observational studies (23 cohort, 32
  case-control)
• Reasonably clear pattern of lower rates
  among active women – median RR 0.8 (20-
  30% lower risk)
• Stronger, more consistent effect for
  postmenopausal women (median RR 0.7)
• Linear trend in two thirds of the studies
  that looked at dose-response
• Lowest risk in lean, physically active women
                  Outline
•   Measuring exposure to physical activity
•   Colorectal cancer
•   Breast cancer
•   Other cancers
•   Recommendations
•   Summary
Physical activity and risk of
      prostate cancer
• At least 36 studies
• Inconsistent findings, median RR 0.9
• Harvard Alumni Study and Health
  Professionals’ Follow-up Study provide
  some support BUT………
• Overall, available epidemiological evidence
  does not support a role for physical
  activity in preventing prostate cancer
  Physical activity and cancer
      risk at other sites
  •   Lung           ‘possible’
  •   Endometrial ‘possible’
  •   Testicular ‘insufficient’
  •   Ovarian        ‘insufficient’
  •   Other (kidney, ovary, testes, liver,
      oesophagus, pancreas, gall-bladder)
      all ‘insufficient’
IARC Handbooks of Cancer Prevention, Vol 6: 2002
Friedenreich (2001) Cancer Epidemiol Biomarkers Prevention 10:287-301
                  Outline
•   Measuring exposure to physical activity
•   Colorectal cancer
•   Breast cancer
•   Other cancers
•   Recommendations
•   Summary
        Recommendations
• 30 to 60 min moderate- to vigorous-
  intensity physical activity on most
  days
• Sustain physical activity over lifetime
• Avoid weight gain
• Maintain BMI between 18.5 and 25.0
• Remember additional benefits from
  physical activity
What is ‘moderate’ intensity?

• For majority of middle-aged and older
  adults, 3 to 6 METs
• What matters is intensity relative to
  one’s capacity
                 .
• 40 to 60% of VO2max (remember that
  .
  VO2max decreases with age)
• Rating of perceived exertion 12-13
Brisk/very brisk walking
(4 to 4.5 METs) typifies
moderate intensity physical
activity for the majority of
middle-aged and older adults
     Modelling the effect of
   increased walking on colon
        cancer incidence
Health Professionals Follow-up Study* data
  – adding 3 h of walking per week to all
    participants suggests a 17% decrease in the
    incidence of colon cancer
  – adding 3 h walking per week to the most
    sedentary men (24%) would reduce incidence
    by only 7%

 Colditz GA et al Cancer Causes Control 1997:8:649-67
 * Giovannucci E et al Ann Internal Med 1995;122:327-34
              Summary I
• Convincing evidence that physical activity
  plays a role in reducing risk of colon and
  breast cancer
• Associations unlikely to be due to other
  healthy behaviours
• Details of dose-response curves and
  optimal amount of activity unclear
• Inactivity is an important, avoidable risk
  factor for these common cancers
               Summary II
• One third of cancer deaths in US can be
  attributed to diet and activity habits†

• Taken together, inactivity and excess
  body weight probably account for one
  third to one fourth of deaths from
  cancer of colon and breast §
 †
   Byers T et al CA Cancer J (2002) 52:92-119
 §
   IARC Handbooks of Cancer Prevention, Vol 6: 2002
                Key References
§ Friedenreich CM, Orenstein MR (2002) Physical activity and
  cancer prevention: etiologic evidence and biological mechanisms.
  J Nutrition 132:345S-64S.
§ Friedenreich CM (2004) Physical activity and breast cancer risk:
  the effect of menopausal status. Ex Sports Sci Revs 32:180-4.
§ International Agency for Research on Cancer (2002). IARC
  Handbooks of Cancer Prevention: weight control and physical
  activity, Vol. 6. Lyon: IARC Press.
§ Lee, I-M (2003) Physical activity and cancer prevention – Data
  from epidemiologic studies. Med Sci Sports Exerc 35:1823-7.
§ McTiernan A (2003) Physical activity, exercise, and cancer:
  prevention to treatment – Symposium overview. Med Sci Sports
  Exerc 35:1821-2 (and associated papers)
§ Slattery ML (2004) Physical activity and colorectal cancer.
  Sports Medicine 34:239-52.

								
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