CHAPTER 4 THE EFFECTS OF PHYSICAL ACTIVITY ON HEALTH …

1 CHAPTER 4 THE EFFECTS OF PHYSICAL ACTIVITY ONHEALTH AND DISEASEC ontentsIntroduction .. 85 Overall Mortality .. 85 Conclusions .. 87 Cardiovascular Diseases .. 87 Cardiovascular Diseases Combined .. 87 Coronary Heart Disease .. 87 CVD Risk Factors in Children .. 91 Stroke .. 102 High Blood Pressure .. 103 Biologic Plausibility .. 110 Atherosclerosis .. 110 Plasma Lipid/Lipoprotein Profile .. 111 Blood Pressure .. 111 Ischemia .. 111 Thrombosis .. 112 Arrhythmia .. 112 Conclusions .. 112 Cancer .. 112 Colorectal Cancer .. 113 Colon Cancer .. 113 Rectal Cancer .. 116 Hormone-Dependent Cancers in Women .. 116 Breast Cancer .. 117 Other Hormone-Dependent Cancers in Women .. 120 Contents, continuedCancers in Men .. 121 Prostate Cancer .. 121 Testicular Cancer .. 124 Other Site-Specific Cancers .. 124 Biologic Plausibility .. 124 Conclusions.

2 124 Non Insulin-Dependent Diabetes Mellitus .. 125 PHYSICAL ACTIVITY and NIDDM .. 125 Biologic Plausibility .. 128 Conclusions .. 129 Osteoarthritis .. 129 PHYSICAL ACTIVITY in Persons with Arthritis .. 129 Biologic Plausibility .. 130 Conclusions .. 130 Osteoporosis .. 130 Biologic Plausibility .. 131 PHYSICAL ACTIVITY and the Prevention of Fractures and Falling .. 132 Conclusions .. 132 Obesity .. 133 PHYSICAL ACTIVITY and Obesity .. 133 Biologic Plausibility .. 134 Conclusions .. 135 Mental HEALTH .. 135 PHYSICAL ACTIVITY and Mental HEALTH .. 136 Biologic Plausibility .. 141 Conclusions .. 141 HEALTH -Related Quality of Life .. 141 Conclusions .. 142 Contents, continuedAdverse EFFECTS of PHYSICAL ACTIVITY .. 142 Types of Adverse EFFECTS .. 142 Musculoskeletal Injuries .. 142 Metabolic Abnormalities .. 143 Hematologic and Body Organ Abnormalities.

3 143 Hazards .. 143 Infectious, Allergic, and Inflammatory Conditions .. 143 Cardiac Events .. 143 Occurrence of Adverse EFFECTS .. 144 Conclusions .. 144 Nature of the ACTIVITY / HEALTH Relationship .. 144 Causality .. 144 Population Burden of Sedentary Living .. 145 Dose .. 146 Conclusions .. 148 CHAPTER Summary .. 149 Conclusions .. 149 Research Needs .. 150 References .. 151 CHAPTER 4 THE EFFECTS OF PHYSICAL ACTIVITY ONHEALTH AND DISEASEI ntroductionThis CHAPTER examines the relationship of physi-cal ACTIVITY and cardiorespiratory fitness to avariety of HEALTH problems. The primary focus is ondiseases and conditions for which sufficient data existto evaluate an association with PHYSICAL ACTIVITY , thestrength of such relationships, and their potentialbiologic mechanisms. Because most of the research todate has addressed the HEALTH EFFECTS of endurance-type PHYSICAL ACTIVITY (involving repetitive use oflarge muscle groups, such as in walking and bicy-cling), this CHAPTER focuses on that type of otherwise specified, the term PHYSICAL activityshould be understood to refer to endurance-typephysical ACTIVITY .

4 Less well studied are the healtheffects of resistance-type PHYSICAL ACTIVITY ( , thatwhich develops muscular strength); when this typeof PHYSICAL ACTIVITY is discussed, it is specified assuch. Much of the research summarized is based onstudies having only white men as participants; itremains to be clarified whether the relationshipsdescribed here are the same for women, racial andethnic minority groups, and people with ACTIVITY is difficult to measure types of PHYSICAL ACTIVITY measures have beenused in observational studies over the last 40 studies have relied on self-reported level ofphysical ACTIVITY , as recalled by people prompted bya questionnaire or interview. A more objectivelymeasured characteristic is cardiorespiratory fitness(also referred to as cardiorespiratory endurance)which is measured by aerobic power (see CHAPTER 2for more information on measurement issues).

5 Somestudies have relied on occupation to classify peopleaccording to how likely they were to be physicallyactive at studies of PHYSICAL ACTIVITY andhealth have compared the ACTIVITY levels of peoplewho have or develop diseases and those who do studies follow populations forward in time toobserve how PHYSICAL ACTIVITY habits affect diseaseoccurrence or death. In case-control studies, groupsof persons who have disease and separate groups ofpeople who do not have disease are asked to recalltheir previous PHYSICAL ACTIVITY . Cross-sectional stud-ies assess the association between PHYSICAL activityand disease at the same point in time. Clinical trials,on the other hand, attempt to alter PHYSICAL activitypatterns and then assess whether disease occurrenceis modified as a from epidemiologic studies can be usedto estimate the relative magnitude or strength of anassociation between PHYSICAL ACTIVITY and a healthoutcome.

6 Two such measures used in this chapterare risk ratio (RR) and odds ratio (OR). For thesemeasures, an estimate of indicates no association,when the risk of disease is equivalent in the twogroups being compared. RR or OR estimates greaterthan indicate an increase in risk; those less indicate a decreased risk. Confidence intervals(CI) reported with estimates of association indicatethe precision of the estimate, as well as its statisticalsignificance. When the CI range includes , theeffect is considered likely to have occurred by chance;therefore the estimate of association is not consid-ered statistically significantly different from the nullvalue of MortalityPersons with moderate to high levels of physicalactivity or cardiorespiratory fitness have a lowermortality rate than those with sedentary habits or86 PHYSICAL ACTIVITY and Healthlow cardiorespiratory fitness. For example, com-pared with people who are most active, sedentarypeople experience between a to a 2-foldincreased risk of dying during the follow-up interval(Slattery and Jacobs 1988; Slattery, Jacobs, Nichaman1989; Leon and Connett 1991; Stender et al.)

7 1993;Sandvik et al. 1993; Chang-Claude and Frentzel-Beyme 1993; Kaplan et al. 1987; Arraiz, Wigle, Mao1992; Paffenbarger et al. 1993).Associations are generally stronger for measuredcardiorespiratory fitness than for reported physicalactivity (Blair, Kohl, Paffenbarger 1989). Blair, Kohl,and Barlow (1993) showed that low levels of cardio-respiratory fitness were strongly associated withoverall mortality for both women (RR = ; 95%CI, ) and men (RR = ; 95% CI, ). The association with PHYSICAL inactivity wasweaker for men (RR = ; 95% CI, ), andthere was no association for women (RR = ; 95%CI, ).Though cardiorespiratory fitness may be thebetter indicator of regular PHYSICAL ACTIVITY , the levelof reported PHYSICAL ACTIVITY has been associated withreduced all-cause mortality. Paffenbarger, Lee, andLeung (1994) evaluated several types of recalledactivity (walking, stair climbing, all sports, moderate-level sports, and total energy expended in ACTIVITY perweek) as predictors of all-cause mortality amongmale Harvard alumni.

8 Among these men, the relativerisk of death within the follow-up period was reducedto with walking 15 or more kilometers per week(reference group, < 5 kilometers/week), to withclimbing 55 or more flights of stairs per week (refer-ence group, < 20 flights/week), to with involve-ment in moderate sports (reference group, noinvolvement), and to with 3 or more hours ofmoderate sports activities per week (reference group,< 1 hour/week). Most importantly, there was a signifi-cant trend of decreasing risk of death across increas-ing categories of distance walked, flights of stairsclimbed, and degree of intensity of sports have also examined age-specific ef-fects of different levels of PHYSICAL ACTIVITY on all-cause mortality. Kaplan and colleagues (1987) haveshown that PHYSICAL ACTIVITY level has an effect ondeath rates among both older and younger from a study of 9,484 Seventh-Day Adventistmen aged 30 years or older in 1958 who werefollowed through 1985 indicated that both moderateand intense levels of ACTIVITY reduced overall risk ofdeath even late in life (Lindsted, Tonstad, Kuzma1991).

9 Both moderate and vigorous levels of activitywere equally protective at age 50 years. The protec-tive effect of high levels of ACTIVITY lasted only untilage 70 , but the protective effect for moderate activitylasted beyond age studies cited thus far in this section assessedphysical ACTIVITY or cardiorespiratory fitness atbaseline only and then followed up for mortality. Astronger test for a causal relationship is to examinethe effect that changing from lower to higher levelsof PHYSICAL ACTIVITY or cardiorespiratory fitness hason subsequent mortality. Two large studies providesuch evidence. Among middle-aged Harvard malealumni who were sedentary in 1962 or 1966, thosewho took up moderately intense sports ACTIVITY dur-ing the study s 11 years of follow-up had a 23 percentlower death rate (RR = ; 95% CI, ) thanthose who remained sedentary (Paffenbarger et ). (By comparison, men who quit smokingduring the interval had a 41 percent decrease indeath rate [RR = ; 95% CI, ].)

10 Men45 84 years of age who took up moderately intensesports extended their longevity on average by ; added years of life were observed in allage groups, including men 75 84 years of age(Paffenbarger et al. 1993).Similar reductions in death rates with increasesin cardiorespiratory fitness were reported for men inthe Aerobics Center Longitudinal Study. Blair andcolleagues (1995) reported a reduction in death ratesamong healthy men (aged 20 82 years) who im-proved their initially low levels of cardiorespiratoryfitness. The men performed two maximal exercisetests an average of years apart; follow-up formortality after the second test occurred an average years later. Among men in the bottom fifth of thecardiorespiratory fitness distribution, those whoimproved to at least a moderate fitness level had a 44percent lower death rate than their peers who re-mained in the bottom fifth (RR = ; 95% CI, ).