UCL RESEARCH DEPARTMENT OF EPIDEMIOLOGY AND PUBLIC HEALTH

There is a lay perception that emotional stress causes heart disease. However, whether and how this might happen is unclear. We measured a stress hormone called cortisol in saliva samples collected 6 times per day to see if it predicted deaths, in particular deaths due to heart disease.

On a normal day, cortisol levels start high in the morning and they decline across the day. We found that a slower decline in salivary cortisol measurements throughout the day appear to be associated with an increased risk in cardiovascular-related death.

Slower declines in salivary cortisol can happen because of low levels of morning or high levels of evening cortisol. We found that morning levels of cortisol were not related to subsequent mortality but high levels of cortisol measured at bedtime were related to cardiovascular deaths. The causes of raised evening levels or flat slopes in cortisol are unknown. They could be related to current stress or reflect long term changes due to chronic stress.