Saliva may tell future health risk
According to research published in Plos One, low levels of antibodies in saliva (sIgA) appear to indicate a greater risk of mortality and could be an early warning sign.
The white blood cells in the blood secrete immunoglobulins (Ig), or antibodies. Ig are proteins that are essential to defend against infectious diseases. The Ig circulate in the body and tag, destroy and/or neutralize bacteria, viruses and other harmful or foreign materials. This is done by coating foreign materials, thus marking them for destruction or neutralization.
In the mucosa of the mouth, nose and gastrointestinal tract is secreted an Ig called Secretory IgA (sIgA) that can be measured in the saliva.
sIgA is the first line of defense against infection at these surfaces and it prevents germs from colonizing. sIgA defends against infections (viral and bacterial) of the upper respiratory tract (URTIs), such as colds and influenza.
However, sIgA levels have to be interpreted in the right context. For example, in the case of dental health, lower levels of sIgA appear to be a risk marker for dental caries and decay, whereas high levels are associated with current oral infection.
Researchers from the University of Birmingham in the UK surveyed adults and wanted to examine associations between secretory immunoglobulin A (sIgA) in saliva and mortality rates in the general population.
The researchers enrolled 639 participants and sampled their saliva in 1995 when they were aged 63 years. Their IgA secretion rate was measured and the mortality rate was follow-up over the following 19 years.
Adjustments were made for gender, household occupational group, smoking, medication usage and self-reported health.
IgA secretion rate was negatively associated with all-cause mortality. Further analysis revealed an underlying association with cancer mortality and, in particular, with non-lung cancers.
Saliva sampling is less invasive than blood sampling. If IgA secretion rate in saliva does prove to be a marker of mortality risk, it could be used by during a general checkup.
Dr. Anna Phillips, from the University of Birmingham, explains: ‘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.’
Dr. Phillips adds that it is not yet known how saliva samples could be used in checkups, as researchers have yet to establish what secretion rate would be considered the threshold level before becoming a cause of concern, otherwise known as the ‘protective level.’
She says that if the level is very low, this could be considered a useful early indicator of risk.
The team hopes to follow up with a larger study to investigate the link with infectious diseases and cancer to get a better understanding of the mechanisms of the findings observed in the study.
