The survey, published in Quality and Safety in Healthcare, showed that half of the doctors were influenced by a patient's age in their decisions on whether to send a patient for tests or prescribe treatment. Patients over 65 were managed differently from those who were younger.
The findings are based on a survey of almost 90 general practitioners, specialists in care of the elderly, and cardiologists from across Southern England and the Midlands.
Participants were specifically quizzed about their intended management of 72 fictional patients with angina, using a specially devised computer programme, and face to face structured interviews.
The fictional patients were all aged between 45 and 92, with varying degrees of severity of heart problems. Head and shoulders photographs of people who had agreed to be the fictional patients were also provided.
Overall, older patients were less likely to be referred to a cardiologist and given an angiogram or exercise tolerance tests as middle aged patients. They were also less likely to be given revascularisation.
But they were significantly more likely to have their medication changed and told to come back at a later date.
Half of the doctors in each of the three professional groups treated older patients differently. Those who were influenced by a patient's age were on average five years older then those who were not.
The face to face interviews revealed various reasons for differences in treatment, some of which related to patients' wishes, potential complications of treatment and the frailty of the individual concerned.
Two doctors deliberately dissociated the influence of these factors from that of old age.
One doctor commented: 'I'd like to think that I would treat the individual. I think generally you have to try and identify from an individual what is in their best interests. I don't think bypass surgery in an 87 year old is in their interests.'