A saliva test could predict how long we have got left to live, scientists claim (file photo)

A saliva test could predict how long we have got left to live.

Researchers found that levels of a particular antibody falls the nearer a person gets to death.

To reach their conclusion, took samples from 639 adults in 1995 and tracked them over 19 years.

They found that the levels of secretory immunoglobin A (IgA) fell the nearer the person got to death.

Antibodies are used by the body to fight infection and are secreted by white blood cells.

The researchers said the chemical appears to be a marker of mortality risk, and is much less invasive than blood sampling.

Testing levels of IgA could be used as way of looking at overall health by professionals as part of a general check-up.

The research was published in the journal PLOS One.

Dr Anna Phillips, from the University of Birmingham, said: ‘There are a number of factors that can affect how well we produce antibodies and maintain their levels.

‘There are some that we have no control over, such as age, heritability or illness, but our general state of health can also affect their levels; stress, diet, exercise, alcohol and smoking can all influence those levels.’

‘Quite how saliva samples could be used in check-ups remains to be seen, as we need to better understand what secretion rate would be considered cause for concern - what we call the protective level.

'We could certainly say that, if found to be extremely low, it would be a useful early indicator of risk.’

The team believe that the next step would be to follow up with a larger longitudinal study, to investigate the link with infectious diseases and the development progression of disease like cancer to provide a greater understanding of the mechanisms behind the association found in the study.

Other methods of predicting how long a person has to live have been developed based on questionaires.

For anyone who can’t wait until the saliva test is developed, an online test called the UK Longevity Explorer has been developed which can determine whether someone will live for the next five years.

The test could be used as way of looking at overall health by professionals as part of a general check-up

The test developed by Swedish scientists and found at ubble.co.uk is aimed at people between 40-70.

It works by answering 11 questions for women and 13 for men and offers a percentage chance of dying in the next five years.

Saliva is increasingly being used as a predictive tool by scientists.

In recent years, tests that claim to be able to predict whether someone is gay or not, is likely to develop Alzheimer’s, and chances of developing various cancers.