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In a study population of 14,998 Harvard male alumni, 681 hypertensives were first diagnosed during a 6-10-year follow-up beginning 16-50 years after college entrance. The study comprised 105,662 man-years of observation of these men who had entered college in 1916-1950, and who were followed from 1962 or 1966 to 1972. Presence or absence of a background of collegiate sports did not influence risk of hypertension in this study population, nor did stair-climbing, walking, or light sports play by alumni. But, alumni who did not engage in vigorous sports play were at 35% greater risk of hypertension than those who did, and this relationship held at all ages, 35-74 years. Higher levels of body mass index, weight gain since college, history of parental hypertension, and lack of strenuous exercise independently predicted increased risk of hypertension in alumni. Men 20% or more over ideal weight-for-height were at 78% greater risk than lighter men. Those who had gained 25+ lbs (c. 11.5+ kg) since entering college were at 60% greater risk than those who had gained less. Alumni with a hypertensive parent were at 83% higher risk than men without such parentage. Contemporary vigorous exercise was inversely related to hypertension risk, but chiefly among alumni overweight-for-height. In the clinical sense, attributable risk estimates ranged from 30% to nearly 50% for the alumni characteristics of overweight, weight gain, parental hypertension, and lack of vigorous exercise. In the community sense, attributable risk of these same characteristics ranged 13-26%. To sum up, vigorous exercise is associated with lower hypertension incidence, and, without necessarily altering body weight-for-height, avoids or reduces fat and promotes muscle; obesity, rather than excess weight-for-height, is associated with higher hypertension incidence; hence, vigorous exercise is appropriate for use as an intervention regimen in the prevention of hypertension.

Risk of first heart attack was found to be related inversely to energy expenditure reported by 16,936 Harvard male alumni, aged 35-74 years, of whom 572 experienced heart attacks in 117,680 person-years of followup. Stairs climbed, blocks walked, strenuous sports played, and a composite physical activity index all opposed risk. Men with index below 2000 kilocalories per week were at 64% higher risk than classmates with higher index. Adult exercise was independent of other influences on heart attack risk, and peak exertion as strenuous sports play enhanced the effect of total energy expenditure. Notably, alumni physical activity supplanted student athleticism assessed in college 16-50 years earlier. If it is postulated that varsity athlete status implies selective cardiovascular fitness, such selection alone is insufficient to explain lower heart attack risk in later adult years. Ex-varsity athletes retained lower risk only if they maintained a high physical activity index as alumni.

In a 22-year followup of 3686 San Francisco longshoremen, a cohort analysis assessed job activity and six personal characteristics in relation to 395 fatal heart attacks. Four cohorts aged 35-44, 45-54, 55-64, and 65-74 in 1951 were studied annually for job shifts affecting energy output and for sudden or delayed death from heart attack by age 75. All subjects underwent multiphasic screening for heavy cigarette smoking, higher blood pressure, history of prior heart disease, obesity, abnormal glucose metabolism, and higher blood cholesterol. The first three of these characteristics added risk of fatal heart attack. The amount of risk varied in the four cohorts. Higher energy output on the job reduced risk of fatal heart attack, especially sudden death, in the two younger cohorts, where less active workers were at threefold increased risk. Lack of this effect in the two older cohorts could imply real differences in their work habits, such as being less energetic in heavy jobs or more energetic in light jobs than the younger cohorts. Or, before the study began, early deaths may have winnowed susceptibles from the two older cohorts. Combined low-energy output, heavy smoking, and higher blood pressure increased risk by as much as 20-fold. By elimination of these adverse influences, this population might have had an 88% reduction in its rate of fatal heart attack during the 22 years.