Paradox of occupational and leisure-time physical activity associations with cardiovascular disease

For more than 70 years, research indicates that physical activity is good for heart health. Epidemiological research in this area began in the 1950s with the studies of Dr Jeremiah N Morris. Morris et al studied how occupations with various levels of physical activity were associated with coronary heart disease (CHD). Morris et al included over 31 000 men employed by the London Transport Executive and examined differences in CHD incidence and CHD death for men who were bus conductors compared with men who were drivers. This early study found that bus conductors, who climbed steps and moved around collecting fares from passengers, had a lower risk of CHD incidence and early CHD death than drivers who spent more time sitting. Morris et al next conducted a similar study with men employed by the Post Office and Civil Service. Postal carriers, who mostly walked, did some stair climbing and light carrying, had a lower risk of CHD and early CHD death than sedentary postal workers, such as telephonists, executives and clerks.