A new study led by Dr Yannan Qin from the Northwest University in China provides insights into why older people were better able to fight off the new strains of ‘bird’ flu than younger people.

Saliva is not normally a topic of polite conversation, but it may be the key to explaining the age and sex bias exhibited by influenza A and other diseases.

“Saliva does more than start the process of digesting certain foods. Saliva also contains germ-fighting proteins that are a first-line defense against infections,” said Dr Qin and colleagues, who report their results in a paper published in the Journal of Proteome Research.

Researchers already knew that levels of certain glycoproteins – proteins with a sugar coating that combat disease-causing microbes – differ with age.

Dr Qin and colleagues took a closer look at how those differences affected vulnerability to influenza A virus.

They collected 180 samples of saliva from men and women of various ages and then assessed the inhibiting and neutralizing activity of saliva against two strains of influenza A (H9N2) virus.

The findings show that glycoproteins in saliva of people age 65 and over were more efficient in binding to influenza than those in children and young adults.

“Seniors, who fought off the bird flu better than the younger groups, might thank their saliva.”

“The research may provide useful information to help understand some age-related diseases and physiological phenomenon specific to women or men, and inspire new ideas for prevention and diagnosis of the diseases by considering the individual conditions based primarily on the salivary analysis,” the researchers said.

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Bibliographic information: Yannan Qin et al. 2013. Age- and Sex-Associated Differences in the Glycopatterns of Human Salivary Glycoproteins and Their Roles against Influenza A Virus. J. Proteome Res., 12 (6), pp. 2742–2754; doi: 10.1021/pr400096w