Thousands of people across the globe were analysed by scientists, who also found optimistic people are also 14 per cent less likely to die early from any cause.

Researchers believe people with positive thoughts are more driven to exercise and have a good diet, protecting their health.

They may also be more able to deal with stress and anxiety, which can put pressure on the heart and cause inflammation.

In the first analysis of its kind, Professor Rozanski and colleagues pooled data from 15 previous studies involving men and women from across the globe, including the UK.

The 230,000 participants came from the US, Europe, Israel and Australia, and were followed for an average of 14 years.

HOW DOES OPTIMISM PREVENT DEATH?

Scientists aren’t yet sure exactly why a sunny disposition may increase lifespan. They believe it’s to do with how we cope with stress – a known risk factor for heart disease, diabetes and cancer.

Stress also compromises our immune system, dampening the body’s ability to cope with infections.

When the brain registers stress, it sends out signals that activate the ‘fight or flight’ response. A flurry of hormones is released, preparing the body to attack or run away. Blood pressure and heart rate soars.

Blood is directed away from the brain, immune and digestive systems and towards the big muscle groups instead.

When we’re locked in a chronic state of stress, arteries get worn down from the heart constantly beating harder and faster, putting us at risk of heart disease.

Studies show this also increases the risk of serious infections and digestive conditions, due to the diversion of blood supply.

One large study from Harvard found pessimists were more likely than optimists to die from cancer, heart disease, stroke, respiratory diseases and infections.

The most recent work, from Mount Sinai St Luke’s Hospital, suggest a healthy outlook simply causes people to eat healthier and exercise more, preventing disease.

There were 35 per cent fewer strokes and heart attacks among those identified as optimists compared to the rest.

Deaths from any cause including cardiovascular disease, cancer, dementia and diabetes were also 14 per cent lower among the optimists.

Levels of optimism were assessed using psychological scales, as well as their overall health.

Professor Rozanski said: ‘Our study was the first meta-analysis, to our knowledge, to assess the association between optimism and clinical outcomes.

‘Findings were consistent with studies that have evaluated the association between optimism and other related medical conditions.’

Previous research has shown being optimistic helps ward off heart failure, Alzheimer’s disease, hardening of the arteries, respiratory disease, infection and various cancers.

Professor Rozanski said this may be due to optimists having a higher tendency to exercise and have a healthy diet while rarely drinking or smoking.

Other studies have reported pessimism can lead to increased inflammation. It can also damage vessels and arteries, raise blood pressure and reduce metabolic function.

Being down in the dumps may even shorten telomeres, protective tips on bits of DNA that have been likened to shoelace caps. Their length is linked to longevity.

Professor Rozanski said: ‘Optimism has long been promulgated as a positive attribute for living.

‘Taken together, the cardiovascular and psychological benefits of optimism make it an attractive new arena for study within the field of behavioural cardiology.

‘Future studies should seek to better define the bio-behavioural mechanisms underlying this association and evaluate the potential benefit of interventions designed to promote optimism or reduce pessimism.’

The team suggest psychological interventions, such as intensive cognitive behavioral therapy (CBT) that reduces symptoms of depression, could be rolled out more widely.

Doctors and nurses should also be pushing positivity in patients – alongside a healthy diet and exercise – more.

Earlier this year another study, based on 70,000 women and 1,500 men in the US, found the most optimistic lived an average 15 percent longer.

The Boston University team suggested they may find it easier to control emotions, protecting against the effects of stress.

They were also significantly more likely to live to 85 compared with the biggest pessimists.

The team at Mount Sinai St Luke’s Hospital, New York, believe interventions that boost positive thoughts could be used to improve health.

Lead author Professor Alan Rozanski said: ‘The findings suggest a mindset of optimism is associated with lower cardiovascular risk and promotion of optimism and reduction in pessimism may be important for preventive health.’

Professor Rozanski, a cardiologist, said stress, depression and loneliness have been linked to cardiovascular disease.

While a sense of well-being is believed to lower risk factors such as high blood pressure and cholesterol.

He said: ‘Specific mindsets, habitual patterns of thinking which influence individuals’ views and interactions, have also been associated with cardiovascular disease risk.’