People with chronic pain during the first year after a heart attack are likely to die within eight years, a study has found.

According to the latest study, published in the Journal of the American Heart Association, heart attack survivors with any kind of moderate to severe pain – even if the pain is not directly related to the heart attack – are still at a high risk of mortality. The risk of death was more than what is caused by smoking.

"Pain causes significant loss of function and may lead to disability, all of which contribute to major, global public health issues. Research indicates that pain is linked to a higher risk of cardiovascular disease and overall death; however, the impact of pain on death after a heart attack has not yet been examined in large studies," study author Linda Vixner explained in a news release.

The study assessed the data of more than 18,000 patients who suffered heart attacks between 2004 to 2013 in Sweden. The participants were below the age of 75. During follow-up visits, the pain levels of the participants were estimated using questionnaires and all-cause mortality was tracked for 8.5 years.

Around 45% of the participants reported moderate or extreme pain one year after a heart attack. Those with moderate pain had a 35% higher chance of death from any cause than those with no pain. The heart attack survivors with extreme pain were at more than twice the risk of death compared to those with no pain during the study period.

In the United States, a heart attack occurs every 40 seconds. The yearly occurrence of new heart attacks is 605,000, while recurrent heart attacks account for 200,000 cases, according to the American Heart Association.

"After a heart attack, it's important to assess and recognize pain as an important risk factor of future mortality. In addition, severe pain may be a potential obstacle to rehabilitation and participation in important heart-protective activities such as regular exercise; reduced or lack of physical activity, in turn, increases risk," Vixner said.

It is also important for patients who experience pain to reduce additional risk factors such as smoking, high blood pressure and high cholesterol levels, the researcher added.