Loneliness and isolation has previously been linked to a lowered immune system, high blood pressure and, ultimately, premature death.
However new evidence suggests that it could also increase a person's risk of stroke by 32% and their risk of a heart or angina attack by 29%.
Experts have now urged people to take further steps to improve their wellbeing and reduce isolation by joining local community groups or volunteering.
Stroke and coronary artery disease are the two leading causes of illness and death in high income countries.
Researchers trawled through data from more than 181,000 adults from 23 different studies published up until May 2015.
They found that 4,628 of them had suffered coronary heart disease ‘events’ - for example, heart attacks, angina attacks, death - and 3,002 had suffered strokes during periods ranging from three to 21 years.
Analysis of the data showed that loneliness was associated with a 29% increased risk of a heart or angina attack and a 32% heightened risk of having a stroke.
The effect size was comparable to that of anxiety and job strain.
Researchers said that it wasn’t possible to exclude the potential impact of other unmeasured factors or reverse causation.
Nevertheless, the findings back public health concerns about the importance of social contact for health and wellbeing, they added.
"Our work suggests that addressing loneliness and social isolation may have an important role in the prevention of two of the leading causes of morbidity in high income countries," they wrote in the study, which was published online in the journal Heart.
In response to the findings, Christopher Allen, senior cardiac nurse for the British Heart Foundation, said: "Social isolation is a serious issue that affects many thousands of people across the UK.
"We know that loneliness, and having few social contacts, can lead to poor lifestyle habits such as smoking which can increase your risk of heart disease and stroke."
He added that although the study suggests there's a physiological link between loneliness and heart problems, this is "not a clear link" and much more research needs to be done to understand if there's definitely a relationship between the two.
"Earlier BHF-funded research has shown an association between social isolation and increased risk of dying, and the BHF continues to fund research exploring how our mental health affects our risk of developing heart problems," he added.
"It’s important for anyone affected by loneliness to remember that they can reach out to their GP for help and advice and also take further steps to improve their wellbeing such as joining a local community group or possibly volunteering in their free time."
Caroline Abrahams, charity director at Age UK, said: "Not only does loneliness make later life unbearably miserable as this research shows it’s awful for our health too.
"We know that lonely older people are more likely to suffer health problems and to require long-term care, have a higher use of medication and need to visit their GP more often.
"This means that loneliness is placing further pressure on the NHS and social care services – making it an issue the Government simply can’t afford to ignore."
She said that with an ageing population, loneliness in later life will continue to increase unless something changes.
"Truly, no one should have no one in our society and the Government must recognise loneliness and isolation in later life as the serious health hazards they are, and work with others, including charities and the NHS, to tackle them," she said.
"That said everyone can help by being a better friend and neighbour and any older person who is feeling lonely or isolated should contact Age UK Advice for free on 0800 169 2081 to find out how our network can help someone who may be feeling alone."
Story continues below...
Great Foods For Heart Health
In a linked editorial, Dr Julianne Holt-Lunstad and Dr Timothy Smith of Brigham Young University, Utah, said that one of the greatest challenges will be to design effective interventions to boost social connections.
"With such rapid changes in the way people are interacting socially, empirical research is needed to address several important questions. Does interacting socially via technology reduce or replace face to face social interaction and/or alter social skills?" they asked.
"Given projected increases in levels of social isolation and loneliness in Europe and North America, medical science needs to squarely address the ramifications for physical health.
"Similar to how cardiologists and other healthcare professionals have taken strong public stances regarding other factors exacerbating [cardiovascular disease]...further attention to social connections is needed in research and public health surveillance, prevention and intervention efforts."