A high level of troponin a protein normally used to exclude the possibility of a heart attack in patients with chest pain may signal a heightened risk of death from any cause within the next couple of years, even in the absence of known or suspected cardiovascular disease, suggests new research.

High cardiac troponin levels are often seen in hospital patients who don't have specific signs of a heart attack, but the clinical significance of this has never been clear, said the researchers from the University of Southampton, UK.

To explore this further, the team tracked the survival of 20,000 hospital patients who had had a troponin blood test for any reason, regardless of the original clinical indication.

The finding, published online in the journal Heart, showed that an abnormally high cardiac troponin level was independently associated with a 76 per cent heightened risk of death, not only from both cardiovascular diseases but also other causes.

In fact, the most common cause of death was cancer (46 per cent), followed by cardiovascular disease (13 per cent). After excluding deaths that occurred within 30 days, a parameter used to define the likelihood that this was associated with the reason for their hospital stay, the link between cardiac troponin and heightened risk of death persisted.

This indicates that this association wasn't driven purely by a short-term risk of death, highlighted the researchers. This is an observational study, and as such, no firm conclusions about cause and effect can be drawn, the researchers said.

They also acknowledged several limitations such as the study was carried out at one hospital.

However, it seems biologically implausible that cardiac troponin level itself poses a heightened risk of death, and more likely that it represents a broad spectrum of health issues, including those as yet undiagnosed, which increase the risk, the researchers noted.

"This study suggests that (cardiac troponin) may have a more general role as a marker of medium-term prognosis outside (heart attack)," they said.

"Further research is required to confirm these findings across multiple settings and to evaluate whether any intervention can adjust the increased risk demonstrated," they add.