Time trends in physical activity among college alumni, 1962-1988.

Little direct evidence exists in the epidemiologic literature to support the widely held belief that an individual's physical activity behavior varies over the years. To provide data, the authors prospectively studied patterns of physical activity among 6,092 Harvard College alumni (average age at the start of follow-up, 43 years) who responded to questionnaires in 1962 or 1966, 1977, and 1988, and who declared themselves free of cardiovascular disease and cancer throughout that period. The median energy expenditure increased between 1962 or 1966 and 1977, but stabilized between 1977 and 1988. However, rank correlation coefficients between estimates of energy expenditure in 1977 and 1988 ranged from 0.36 to 0.41 for the various age groups (compared with 0.81-0.84 for the Quetelet index, and 0.60-0.65 for the current number of cigarettes smoked per day), implying that physical activity at the individual level was not constant. For 4,238 alumni for whom data on collegiate sports participation were available, the rank correlation coefficients between collegiate activity and alumni activity 1-7 decades later were even lower, ranging from 0.05 to 0.17 (compared with 0.31-0.58 for the Quetelet index). Thus, physical activity assessed over a short time period in an individual may not be a valid proxy for activity over the long term. The characteristics that distinguished alumni who consistently expended less than 1,000 kcal/week (in climbing stairs, walking, and playing sports) in 1962 or 1966, 1977, and 1988 from those who consistently expended greater than 2,500 kcal/week were as follows: at baseline, older age, overweight, and cigarette smoking; and during college, not having been a varsity athlete and fewer hours playing sports.     

Heart disease risk factors, diabetes, and prostatic cancer in an adult community

The authors studied the association between heart disease and prostatic cancer in Rancho Bernardo, California, from August 1972 to June 1987. During a 14-year follow-up of 1,776 men aged 50-84 years, 100 cases of prostatic cancer were identified, of which 54 were incident. Systolic blood pressure, cigarette smoking, and plasma cholesterol levels in cases did not differ from those in noncases. After adjustment for age and on multivariate analysis, incident cases of prostatic cancer had a nonsignificantly higher frequency of reported heart disease at baseline. History of diabetes was inversely associated with total prostatic cancer (age-adjusted estimated relative risk = 0.2, 90% confidence interval: 0.0-0.8; multivariate-adjusted relative risk = 0.3, 90% confidence interval: 0.1-1.0). The association between heart disease and prostatic cancer is compatible with diagnostic detection bias. The inverse association between diabetes and prostatic cancer is compatible with a cancer-promoting role for endogenous testosterone, the level of which is lower in diabetics, or a risk-reducing effect of antidiabetic diet or drug therapy.     

Relationship of lipoprotein(a) levels to physical activity and family history of coronary heart disease

OBJECTIVES: This study evaluated the association of physical activity with serum lipoprotein(a) [La(a)] levels in individuals according to whether they had a family history of coronary heart disease (CHD). METHODS: Lp(a) levels in 332 healthy Spanish men aged 20 to 60 years were measured. Physical activity and family history of CHD were assessed. RESULTS: For men with a family history of CHD, the odds ratio for Lp(a) levels above the median value was 0.13 (95% confidence interval = 0.03, 0.50) in very active men (energy expended in physical activity > 300 kcal/day) compared with active men (energy expended in physical activity < 300 kcal/day). CONCLUSIONS: Regular daily physical activity in individuals with a family history of CHD could be useful for controlling Lp(a) levels.     

Leisure time physical activity in the Framingham Offspring Study. Description, seasonal variation, and risk factor correlates

Self-reported leisure time physical activity was analyzed for 1,598 men and 1,762 women aged 20-69 years in the Framingham Offspring Cycle 2 exam in 1979-1983. Walking for pleasure was generally the most common physical activity for both sexes throughout the year. Substantial seasonal variation was noted for the most common activities: gardening, carpentry, lawn mowing, golf, and running for men; and gardening, swimming, health club exercise, dancing, and bicycling for women. Both sexes expended more kilocalories in physical activities in summer than in winter (p less than 0.001). Frequency of participation in activities sufficient to induce perspiration was associated with frequency of participation in at least one hour of conditioning (greater than or equal to 7.5 kilocal/minute) activities per week (p less than 0.001). Based on age-adjusted mean levels, higher high density lipoprotein cholesterol, lower heart rate, lower body mass index and fewer cigarettes smoked per day were consistently observed across four quartiles of increasing physical activity levels (p less than 0.01). Men who participated in at least one hour of conditioning activities per week had significantly different mean levels for these four risk factors than men who reported less than one hour of such activities per week (p less than 0.001). Results substantiate previous reports of an inverse relation between physical activity levels and cardiovascular risk, and suggest seasonal variation in activity levels should be considered in future studies which explore the relation between physical activity and cardiovascular disease.     

Physical Activity and Reduced Breast Cancer Risk: A Multinational Study

We evaluated the association between physical activity and breast cancer risk among 1,463 breast cancer cases and 4,862 controls in a multinational study. All subjects were asked how many times and for how long they exercised or engaged in strenuous physical labor per week. We used multivariate logistic regression to assess the association between physical activity and breast cancer risk. For all subjects combined, the multivariate-adjusted odds ratio was 50% lower (95% confidence interval = 0.4–0.6) for women who reported physical activity once per week or more after adjusting for age, race, body mass index, and pack years of smoking compared to those who reported physical activity less than once per week. Women who reported physical activity 3 times/wk or more did not gain any additional reduced risk. The amount of time spent in physical activity per session was also significantly associated with reduced risk. All ethnic groups examined including Caucasian-Americans, African-Americans, Hispanic-Americans, Tunisian-Arabs, and Polish-Caucasians were at 35% or greater reduced risk for breast cancer if they were physically active for more than 30 minutes per week. Our study shows that physical activity may reduce breast cancer risk regardless of race, weight category, or family history of breast cancer.     

Incidence of surgically treated benign prostatic hypertrophy and of prostate cancer among blacks and whites in a prepaid health care plan.

The incidence of surgically treated benign prostatic hypertrophy and of prostate cancer was examined to December 1987 in 14,897 men (2,175 blacks and 12,722 whites) who received multiphasic health checkups during 1971-1972 while members of the Kaiser Permanente Medical Care Program (San Francisco-Oakland, California). Prostate cancer incidence was higher in blacks than in whites for all age groups (age-adjusted relative risk (RR) = 1.8, 95% confidence interval (CI) 1.4-2.3). The incidence of benign prostatic hypertrophy was somewhat higher in blacks than in whites until age 65 years, after which it was higher in whites. In contrast to the risk of prostate cancer, the age-adjusted risk of benign prostatic hypertrophy was the same for blacks as for whites (RR = 1.0, 95% Cl 0.8-1.2).     

Physical activity and cardiovascular disease risk in middle-aged and older women.

The authors investigated the relation between physical activity and cardiovascular disease (CVD) in women by following 1,564 University of Pennsylvania alumnae (mean age, 45.5 years), initially free of CVD, from 1962 until 1993. Energy expenditure was estimated from the daily number of flights of stairs climbed and blocks walked as well as the sports played and was categorized into approximate thirds (<500, 500-999, > or = 1,000 kcal/week). During 35,021 person-years, 181 CVD cases were identified. After adjustment for coronary risk factors, the relative risks of CVD were 0.99 (95% confidence interval (CI): 0.69, 1.41) and 0.88 (95% CI: 0.62, 1.25) for women who expended 500-999 and > or = 1,000, respectively, compared with <500 kcal/week (p for trend = 0.45). Only walking was found to be inversely related to CVD risk (p for trend = 0.054). Compared with women who walked <4 blocks/day, the relative risks of CVD were 0.84 (95% CI: 0.59, 1.19) and 0.67 (95% CI: 0.45, 1.01) for women who walked 4-9 and > or = 10 blocks/day, respectively. Finally, an interaction (p = 0.023) between body mass index and physical activity on CVD risk was observed, with an inverse association only for leaner (<23 kg/m2) women. These data showed no overall association of physical activity with CVD risk in women. However, walking > or = 10 blocks/day (approximately 6 miles (9.7 km)/week) was associated with a 33% decreased risk. One explanation for this finding may be that walking was reported more precisely than other kinds of activities.     

Prostate cancer, benign prostatic hyperplasia and physical activity in Shanghai, China

BACKGROUND: Studies suggest that increased levels of physical activity might decrease the risk of prostate cancer. We ascertained lifetime measures of activity in a population-based case-control study of prostate cancer in Shanghai, China to investigate physical activity in a population where the incidence of prostate cancer is low but rising. METHODS: In all, 238 men with prostate cancer, diagnosed 1993-1995, were identified through a rapid reporting system. A second group of 206 men with benign prostatic hyperplasia (BPH) was matched to prostate cancer cases, and 471 age-matched and population-based controls were identified from urban Shanghai. Through personal interviews, we ascertained all daily, occupational, and recreational activities at ages 20-29, ages 40-49, and in 1988 to generate hours spent sleeping, sitting, in moderate activity, and in vigorous activity. Time spent per week in different activities was converted to metabolic equivalents (MET-h) and energy expended. RESULTS: Time spent in, MET-h of, and energy expended in physical activities were not consistently related to either prostate cancer or BPH when compared to controls. Few men reported regular vigorous activity. Occupational activity, based on an energy expenditure index using job titles, was suggestively associated with a decreased risk of BPH, but not associated with prostate cancer. Associations did not vary according to age or stage of prostate cancer at diagnosis. CONCLUSIONS: Our results, based on regular physical activity, occupational activity, hours in activities, MET-h, and energy expended, did not support a protective role of physical activity in prostate cancer or BPH for men in a low-risk population.     

Physical activity and incidence of postmenopausal breast cancer

Whether physical activity reduces the risk of postmenopausal breast cancer is uncertain; few studies have addressed this issue. We examined the association of leisure physical activity with breast cancer incidence among 37,105 postmenopausal participants in the Iowa Women's Health Study. Women reporting the highest level of physical activity at baseline compared with women with the lowest level of activity had an age-adjusted relative risk of breast cancer of 0.92 (95% confidence interval = 0.80-1.05). Women reporting any regular leisure-time physical activity had a relative risk of 0.97 (95% confidence interval = 0.87-1.08) compared with those reporting no such regular physical activity. Adjustment for potential confounders did not appreciably alter the findings. There is little evidence from this study that physical activity later in life is associated to any appreciable extent with breast cancer incidence.     

The "weekend warrior" and risk of mortality

Physical activity improves health, and current recommendations encourage daily exercise. However, little is known about any health benefits associated with infrequent bouts of exercise (e.g., 1-2 episodes/week) that generate the recommended energy expenditure. The authors conducted a prospective cohort study among 8,421 men (mean age, 66 years) in the Harvard Alumni Health Study, without major chronic diseases, who provided details about physical activity on mailed questionnaires in 1988 and 1993. Men were classified as "sedentary" (expending <500 kcal/week), "insufficiently active" (500-999 kcal/week), "weekend warriors" (>/=1,000 kcal/week from sports/recreation 1-2 times/week), or "regularly active" (all others expending >/=1,000 kcal/week). Between 1988 and 1997, 1,234 men died. The multivariate relative risks for mortality among the sedentary, insufficiently active, weekend warriors, and regularly active men were 1.00 (referent), 0.75 (95% confidence interval (CI): 0.62, 0.91), 0.85 (95% CI: 0.65, 1.11), and 0.64 (95% CI: 0.55, 0.73), respectively. In stratified analysis, among men without major risk factors, weekend warriors had a lower risk of dying, compared with sedentary men (relative risk = 0.41, 95% CI: 0.21, 0.81). This was not seen among men with at least one major risk factor (corresponding relative risk = 1.02, 95% CI: 0.75, 1.38). These results suggest that regular physical activity generating 1,000 kcal/week or more should be recommended for lowering mortality rates. However, among those with no major risk factors, even 1-2 episodes/week generating 1,000 kcal/week or more can postpone mortality.     

Cigarette smoking, obesity, and benign prostatic hypertrophy: a prospective population-based study.

The authors examined the relation of smoking and obesity to surgically treated benign prostatic hypertrophy in a prospective study of white men aged 40-79 years who were first examined in 1972-1974 and were followed for an average of 12 years. After exclusion of those whose surgery preceded assessment of smoking and obesity and those who had prostate cancer, there were 165 cases of benign prostatic hypertrophy among 929 men. Age-adjusted relative risk of benign prostatic hypertrophy in current or previous smokers compared with nonsmokers was 1.1 (95% confidence interval 0.8-1.6). Age-adjusted relative risk of benign prostatic hypertrophy in the most obese tertile (body mass index (kg/m2) greater than 26.75) compared with the remainder showed a relative risk of 0.9 (95% confidence interval 0.6-1.4). Multivariate analysis also failed to show a relation between cigarette smoking or obesity and the development of surgically treated benign prostatic hypertrophy.     

Physical activity and risk of lung cancer.

BACKGROUND: Physical activity has been proposed to decrease lung cancer risk; however, few data are available. Further, no studies have examined specific kinds and intensities of activities. METHODS: We conducted a prospective cohort study among 13 905 male Harvard University alumni (mean age, 58.3 years), free of cancer. Men reported their walking, stair climbing and participation in sports or recreation on baseline questionnaires in 1977, and the occurrence of lung cancer on follow-up questionnaires in 1988 and 1993. Death certificates were obtained for decedents through 1992 to determine lung cancers not previously reported. RESULTS: During follow-up, 245 men developed lung cancer. Adjusting for age, cigarette smoking, and body mass index, the relative risks of lung cancer associated with <4200, 4200-8399, 8400-12 599 and > or =12 600 kJ/week of estimated energy expenditure at baseline were 1.00 (referent), 0.87 (95% CI: 0.64-1.18), 0.76 (95% CI: 0.52-1.11), and 0.61 (95% CI: 0.41-0.89), respectively; P trend = 0.0008. Similar trends were observed among non-smokers or former smokers in 1977 (82.7% of men) as well as among those who smoked >20 cigarettes a day in 1977 (8.0%), although the findings in the latter group were not statistically significant, possibly due to the small number. Walking, climbing stairs and participating in activities of at least moderate intensity (> or =4.5 MET, or multiples of resting metabolic rate) were each inversely associated with lung cancer risk, independent of the other activity components. However, light intensity activities (<4.5 MET) did not predict lung cancer risk. CONCLUSIONS: These data indicate that physical activity may be associated with lower risk of lung cancer among men. An energy expenditure of 12 600 kJ/week, achievable by perhaps 6-8 hours of at least moderate intensity physical activity, may significantly lower risk. Further studies are required to confirm these observations.     

Occupational and leisure-time physical activity and risk of colon cancer by subsite

OBJECTIVE: Studies of physical activity and colon cancer risk by anatomic site have provided inconsistent results. METHODS: We analyzed data from a population-based case-control study conducted in Iowa involving 685 colon cancer cases and 2434 control subjects. RESULTS: Among those who reported recreational activity more than twice per week, a 30% risk reduction of colon cancer was observed for all sites with a 40% risk reduction for cancer of the right colon. Occupational physical activity was also associated with a reduced risk of colon cancer. The risk was the lowest for those with both high occupational and recreational physical activity (odds ratio, 0.5; 95% confidence interval, 0.3-0.8). CONCLUSIONS: Increased physical activity was inversely associated with colon cancer risk. The inverse associations were stronger for the right than for the left colon.     

不同强度职业性体力活动对子宫肌瘤的影响

目的 探讨职业性体力活动与中老年女性子宫肌瘤(UL)危险性的关系.方法 采用以医院为基础的病例对照研究方法.病例由35～62岁的292例UL患者组成,对照由同期入住相同医院按年龄进行频数匹配的292例非UL患者组成.采用自行设计的健康状况调查表对研究对象进行调查,内容包括人口学特征、生活方式以及疾病既往史等.同时还采用国际体力活动调查表(IPAQ)对研究对象的体力活动情况进行调查,将每周进行的不同强度的体力活动所花费的时间转换成代谢当量(MET)和能量消耗.应用多因素Logistic回归分析估计不同强度的职业性体力活动与UL关联的比值比(OR)及其相应的95％可信区间(CI).结果 两组研究对象年龄、婚姻状况、文化程度及家庭经济收入差异均无统计学意义(P＞0.05).不过,初潮年龄≥17岁组的病例(30.82％)显著地低于对照(43.49％) (P=0.007);并且经常参加体育锻炼的病例(28.42％)也明显低于对照组(40.41％) (P=0.01).调整了多种潜在性混杂因素后,总能量消耗增加可使发生UL的危险性降低,与能量消耗为最低四分位数相比较,第3个四分位数发生UL的OR为0.456 (95％CI:0.280～0.743,P=0.002).在轻度体力活动中,能量消耗为最高四分位数发生UL的危险性显著降低(OR=0.657,95％CI:0.073～0.899,P=0.036).同样,中度体力活动的能量消耗也与UL呈负相关(OR=0.501,95％CI:0.332-0.997,P=0.002).然而,在重度体力活动中,能量消耗与发生UL的危险性无关(P=0.911).结论 倡导中老年女性进行适度的体力活动,可有效地预防UL的发生.     

The effect of physical activity on breast cancer risk: A cohort study of 30,548 women

Background: In epidemiological studies abundant physical activity has been related to decreased breast cancer risk, though the results have been inconsistent. The purpose of this paper was to study the association of physical activity at leisure and commuting to work and incidence of breast cancer. Methods: The study cohort consisted of 30,548 female participants of the Finnish adult health behaviour survey, based on annual random samples of Finns aged 15–64, collected in 1978–1993. By the end of 1995, 332 breast cancer cases had been diagnosed in the cohort. Relative risks of breast cancer were adjusted for age at survey, body mass index (BMI), education, length of follow-up, parity and age at first birth using Poisson regression models. Results: Compared to women exercising less than once a week, the adjusted relative risk of breast cancer for women exercising once a week was 0.80 (95% confidence interval (CI): 0.58–1.10), for women exercising 2–3 times per week 0.92 (95% CI: 0.78–1.22) and for women exercising daily 1.01 (95% CI: 0.72–1.42). Women who reported commuting, walking or bicycling to work 30 min or more daily had slightly lower adjusted risk of breast cancer (RR: 0.87, 95% CI: 0.62–1.24) than women working at home, being unemployed or driving a car to working place. Conclusion: Although a small protective effect of regular physical activity for breast cancer incidence was found in physical activity when commuting to work, the role of the physical activity in breast cancer prevention is still an open question.     

Alcohol consumption and risk of prostate cancer: The Harvard Alumni Health Study

BACKGROUND: Although many studies suggest that consumption of alcohol increases the risk of several site-specific cancers, the evidence remains unclear for prostate cancer. Few data exist on beverage-specific associations as well as lifetime patterns of alcohol consumption and prostate cancer risk. METHODS: We prospectively followed 7612 Harvard alumni (mean age 66.6 years) from 1988 through 1993, during which 366 cases of incident prostate cancer occurred. Self-reported alcohol consumption was assessed at baseline from wine, beer, and liquor intake. Previous assessments during college and in 1977 were also available. RESULTS: Overall, the mean total alcohol consumption in 1988 was 123.1 g/week, of which 28.6% was from wine, 15.8% from beer, and 55.6% from liquor. Compared to men reporting almost never drinking alcohol in 1988, the multivariate relative risks (95% CI) for 1 drink/month to < 3 drinks/week, 3 drinks/week to < 1 drink/ day, 1 to < 3 drinks/day, and > or = 3 drinks/day were 1.33 (0.88-2.01), 1.65 (1.12-2.44), 1.85 (1.29-2.64), and 1.33 (0.86-2.05), respectively. Wine or beer consumption was unassociated with prostate cancer; however, moderate liquor consumption was associated with a significant 61-67% increased risk of prostate cancer (P, non-linear trend < 0.001). Men initiating alcohol consumption between 1977 and 1988 had a twofold increased risk of prostate cancer compared to men with almost no alcohol consumption at both times. CONCLUSIONS: In contrast to the majority of previous studies, we found a positive association between moderate alcohol consumption and the risk of prostate cancer. Liquor, but not wine or beer, consumption was positively associated with prostate cancer.     

Relation of physical activity to risk of testicular cancer

In North America and most Western European countries, testicular cancer is often cited as the most common cancer among young and middle-aged men, and yet few studies have examined the relation between modifiable factors and testicular cancer risk. Data collected between 1995 and 1996 in Ontario, Canada, as part of the Enhanced Cancer Surveillance Study were used to examine the relation between the frequency of recreational, and intensity of occupational, physical activity at various life periods, including cumulative and averaged lifetime activity and risk of testicular cancer. Analysis of 212 cases and 251 controls revealed that relatively high frequency of participation in moderate and strenuous recreational activity in the midteens may have an adverse effect on risk of testicular cancer (odds ratio = 2.36, 95% confidence interval: 1.20, 4.64 for moderate activity of greater than five times a week compared with three times or less a month and odds ratio = 2.58, 95% confidence interval: 1.14, 5.85 for strenuous activity of greater than five times a week compared with less than once a month). Moderate or strenuous occupational demands in one's 20s also increased risk of disease.     

Fruit and vegetable intakes and risk of colorectal cancer in the NIH-AARP diet and health study

The authors examined the associations between fruit and vegetable intakes and risk of colorectal cancer in the NIH-AARP Diet and Health Study. Diet was assessed with a food frequency questionnaire at baseline. Relative risks and 95% confidence intervals were estimated by using the Cox proportional hazards model. During 5-year follow-up of 488,043 men and women aged 50-71 years, 2,972 incident colorectal cancer cases were identified. The respective 10th and 90th percentiles of total fruit and vegetable intake (servings/1,000 kcal per day) were 1.4 and 5.2 for men and 1.8 and 6.5 for women. Compared with that for the lowest quintile of vegetable intake, the multivariate relative risk for the highest quintile was 0.82 (95% confidence interval: 0.71, 0.94) for men and 1.12 (95% confidence interval: 0.90, 1.38) for women. Increased risk of colorectal cancer was observed for very low intake of total fruits and vegetables by men (multivariate relative risk for <1 vs. > or =2.0 servings/1,000 kcal per day = 1.26, 95% confidence interval: 1.03, 1.54). Among subgroups of vegetables, green leafy vegetables were associated with a lower risk of colorectal cancer for men (multivariate relative risk for the highest quintile vs. the lowest = 0.86, 95% confidence interval: 0.74, 0.99). Intake of fruits was not related to risk of colorectal cancer in men or women.     

Dietary fat,calories, and the risk of breast cancer in postmenopausal women: a prospective population-based study.

We tested the hypothesis that a high-fat diet increases the risk of breast cancer in a population-based study of 590 women aged 40-79 years who were without known breast cancer when they provided a quantitative 24-hour diet recall. Fifteen postmenopausal women were diagnosed with incident breast cancer during the next 15 years (approximately 7600 person-years of follow-up). These women had significantly higher age-adjusted intake of all fats (monounsaturated, polyunsaturated, and saturated), and oleic, linoleic, and linolenic acids, with a stepwise increase in risk across tertiles of intake. Fat intake was associated with total calories, protein, and carbohydrates, and women with incident breast cancer consumed more calories, protein, and carbohydrates than did other subjects. When each nutrient variable (calories, fats, protein, and carbohydrates) was adjusted for age, body mass index, age at menopause, parity, and alcohol consumption, the strongest risks for incident breast cancer were associated with total calories (relative risk per standard deviation = 2.72, 95% confidence interval = 1.51-4.89, p = 0.002) and total fats (relative risk per standard deviation = 2.01, 95% confidence interval = 1.19-3.41, p = 0.01). Fat composition of the diet, expressed either as percent of energy or as fat intake adjusted for calories by regression analysis, was not significantly associated with risk of breast cancer. These results support the hypothesis that total calorie consumption, as well as dietary fat consumption, is a risk factor for breast cancer in postmenopausal women, and parallel observations in animal models.