The Science

The importance of the salivary glands – and saliva – tends to go unnoticed until the glands malfunction. The consequences are severe and impact greatly on quality of life. Symptoms may start with a constant thirst, difficulty in speaking, eating, tasting and swallowing foods and progress to tooth decay and oral infections.¹ The most common salivary gland disorder is xerostomia, which is the subjective feeling of dryness throughout the mouth.

The prevalence of xerostomia in population-based studies ranges from 10 to 46%, with a lower prevalence for men than women.² Salivary flow rate patterns demonstrate both daily and seasonal variation, with peaks in mid-afternoon and higher flow rates in the winter than in the summer. During sleep, saliva flow rate is minimal.³ People who complain of dry mouth do not necessarily have a very low flow rate; conversely, those with a low unstimulated flow rate do not always complain of dry mouth. It is therefore of greater significance to establish whether or not the flow rate has changed adversely in a particular individual.⁴

Reduced salivary flow is due to hypofunction of the salivary glands. This may be reversible, due to anxiety, acute infection, dehydration or the effects of some drugs. There are also some permanent causes of xerostomia such as congenital abnormalities, Sjögren’s syndrome, HIV/AIDS and the result of head and neck irradiation. However, xerostomia is most commonly associated with the use of xerogenic drugs. More than 400 medicines induce salivary gland hypofunction, including tricyclic antidepressants, antihistamines, certain antihypertensives and drugs with sympathomimetic actions (e.g. some bronchodilators).⁵

In the past, it was commonly believed that dry mouth and declining salivary function were purely a natural consequence of aging. While it is true that salivary gland dysfunctions are more prevalent in older populations, studies suggest that salivary gland dysfunction is due to a combination of aging per se and the higher incidence of chronic illnesses and the greater use of drugs by the aging population – both of which can impact the production of saliva.⁶

Published Research