BACKGROUND:

Cardiovascular disease accounts for 43 percent of all deaths in the United States. Hypertension affects as many as 50 million Americans, however the causes of essential hypertension are not well known. A new CVD risk factor ("job strain") has emerged as a potential major cause of essential hypertension. By 1995, over 20 studies had found significant positive relationships between "job strain" and CVD, coronary heart disease, all-cause mortality or hypertension. "Job strain" is defined as high psychological workload demands combined with low"decision latitude". An expanded concept of "job strain" which included low workplace social support ("iso-strain") was developed and examined in the study.

Important questions remained to be answered about "job strain", CVD and hypertension. In most studies, "job strain" was only measured at one point in time, while, in fact, cumulative exposure to "job strain" was believed to be the risk factor. In addition, most studies relied on self-report measures of "job strain". Also, no studies specifically examined risk of stroke and "job strain".

DESIGN NARRATIVE:

Data from the Cornell University cohort study of Psychosocial Factors and Cardiovascular Disease and the Columbia University-Northern Manhattan Stroke Study were analyzed. The study had five specific aims, including to determine whether: blood pressure levels were associated with cumulative exposure to "job strain"; differences in blood pressure increases were associated with an objective measure of "job strain"; increased risk of stroke was associated with an objective measure of "job strain"; changes in psychological variables over time were associated with job characteristics; changes in CVD risk factors (other than hypertension) were associated with job characteristics.

Paul Landsbergis also constructed measures of cumulative exposure to "job strain" and determined their association with blood pressure, and analyzed the association between job characteristics and change in psychological variables and cardiovascular disease (CVD) risk factors.