June Davison, senior cardiac nurse at the British Heart Foundation, said more research was needed to understand the effects of second-hand smoke.

BBC: Smoking 'poses bigger risk to women'

"The study also reinforces what has been identified by previous research, that stress at work is often associated with unhealthy behaviours such as smoking, lack of exercise and a poor diet - all which can impact on heart health, " said June Davison.

BBC: Stress seems to produce biochemical changes