Fit and healthy people who worry about developing an illness may be increasing their risk of heart disease by unnecessarily fretting over their health, research suggests.

A study of more than 7,000 people over 12 years found that those with health anxiety at the start of the study were about 70% more likely to develop heart disease than those without that state of mind. Additionally, the researchers found that the higher the reported anxiety, the higher the risk of heart disease.

Anxiety is a known risk factor for heart disease but the Norwegian authors of the paper believe it is the first to look specifically at health anxiety, which is characterised by a persistent preoccupation with having or acquiring a serious illness and seeking medical help, despite the absence of any physical disease.

The findings, published in BMJ Open on Thursday, suggest that far from health anxiety protecting people from heart disease through increased monitoring and frequency of checkups, it may have the opposite effect.

The lead author, Dr Line Iden Berge, from the division of psychiatry at Sandviken University hospital in Bergen, Norway, said: “We hypothesised that people with health anxiety would have reduced risk because they would take better care of themselves.

“The results suggest it’s better, instead of worrying about what’s going on with your body and running to the doctor for any physical health problem, to seek a proper diagnosis and help for the anxiety disorder.”

The study analysed 7,052 participants in the long-term collaborative research project Norwegian Hordaland health study, all of whom were born between 1953 and 1957.

They filled in questionnaires about their health, lifestyle and educational attainment and had a physical checkup between 1997 and 1999.

Levels of health anxiety were assessed using a validated scale and the top 10% of the sample – 710 people – were considered to have health anxiety.

The heart health of all the participants was tracked up to the end of 2009. Anyone who received treatment for, or whose death was linked to, coronary artery disease occurring within a year of entering the study, was excluded on the grounds that they might already have been ill.

In all, 234 (3.3%) of the entire sample had an ischaemic event – a heart attack or bout of acute angina – during the monitoring period. But the proportion of those succumbing to heart disease was twice as high (just over 6%) among those who displayed health anxiety compared with those who did not (3%).

After taking account of other potentially influential factors, those with health anxiety at the start of the study were found to be 73% more likely to develop heart disease than those who did not have anxiety at the outset.

As it was an observational study, no firm conclusions can be drawn about cause and effect. Limitations include the frequent co-existence of health anxiety with other mental health issues, making it hard to differentiate, and the fact that the health anxiety index relies on self-reported symptoms and does not discern between imagined illness and more legitimate reasons for concern.

Emily Reeve, senior cardiac nurse at the British Heart Foundation, said: “It’s natural for people to worry if they feel they might be unwell. But anxiety and stress can trigger unhealthy habits, such as smoking or eating badly, which put you at greater risk of heart disease.

“While we don’t know if the worried well are directly putting themselves at risk of a heart attack, it’s clear that reducing unnecessary anxiety can have health benefits. If you are experiencing health anxiety, speak to your doctor.”