Lower levels of antibodies in saliva are associated with an elevated risk of mortality and could be an early indicator of risk, researchers from University of Birmingham have found.
The team examined associations between secretory immunoglobulin A (IgA), the common antibody found in saliva, and mortality rates in the general population.
Immunoglobulins, or antibodies, are proteins secreted by white blood cells and are essential for combating infectious disease.
The researchers found a negative association between IgA secretion rate and all-cause mortality.
Further analysis revealed that the all-cause association was due to an underlying association with cancer mortality and, in particular with non-lung cancers.
There are a number of factors that can affect how well we produce antibodies and maintain their levels.
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"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," explained Anna Phillips from University of Birmingham.
For the study, 639 adults, from the eldest cohort of the West of Scotland Twenty-07 Study took part in the study.
Participants, aged 63-years old at the time of saliva sampling in 1995, had their IgA secretion rate measured and the mortality rate was tracked over the following 19 years.
"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," Phillips added.
We could certainly say that, if found to be extremely low, it would be a useful early indicator of risk, the authors added.
The study was published in the journal PLOS ONE.