Socioeconomic status and stress-related biological responses over the working day

The influence of low socioeconomic status on cardiovascular disease may be mediated in part by sustained activation of stress-related autonomic and neuroendocrine processes. We hypothesized that low socioeconomic status would be associated with heightened ambulatory blood pressure and cortisol output over the working day.

One hundred eight men and 94 women from the Whitehall II epidemiological cohort participated. Blood pressure and heart rate were monitored every 20 minutes over a working day and evening, and salivary cortisol was sampled on waking up and at 2-hour intervals. Measures were also taken under resting laboratory conditions. Socioeconomic status was indexed by grade of employment.

Resting blood pressure, heart rate, and cortisol did not differ by grade. Ambulatory systolic pressure was greater in the morning in the lower (128.9 +/- 15.7 mm Hg) than the intermediate (122.6 +/- 12.5 mm Hg) and higher grades (123.3 +/- 12.7 mm Hg) after adjustment for age, sex, smoking, and alcohol intake (p =.019). Heart rate was also raised in the morning in the lower grade participants. Differences in morning systolic pressure and heart rate were independent of concurrent physical activity. Cortisol concentration was greater in lower than higher grade men (9.54 +/- 4.1 vs. 7.38 +/- 2.8 nmol/liter, p =.008) but was more elevated in higher than lower grade women (7.84 +/- 2.5 vs. 6.35 +/- 1.9 nmol/liter, p =.014). Differences remained significant after adjustment for age, time of awakening, smoking, and alcohol intake.

Socioeconomic differences in blood pressure and cortisol may reflect stress-related activation of biological pathways that contribute to variations in disease risk.