2013). Healthy ageing may affect gastric emptying of solid and liquid foods. In frail

elderly, compared to non-frail elderly, gastric emptying of liquids was found to be

enhanced, whereas gallbladder emptying and oro-cecal transit times were similar in

two groups (Serra-Prat et al. 2013; Bai et al. 2016). Decreased rectal compliance and

rectal sensation associated with healthy ageing often leads to constipation. Rémond

et al. (2015) found that bicarbonate and pepsin enzyme concentrations in the

stomach, as well as lipase, chymotrypsin, and amylase amounts in the duodenal

fluid, were lower among the healthy elderly subjects than younger adults. However,

bile acid secretion was not affected by ageing. According to Demir et al. (2017),

rectal incontinence due to impaired sphincter functions and dementia is one of most

frequent GI tract problems in the elderly, e.g., approx. 3% in people living at home

and 20% to 50% in community-dwelling and nursing homes, respectively. Further,

these authors observed that polypharmacy medications are important risk factors for

urinary and/or rectal incontinence. In view of these observations, it appears that

defective gastrointestinal secretions and functional disorders of the GI tract can be

the important risk factors causing alterations in food digestion and drug absorption in

the geriatric population.

GI tract is one of the most important immune function regulator organs in

the body.

The gut lymphatic system network plays a vital role in maintaining extracellular

homeostasis, lipid absorption, and optimizing immunity against pathogenic bacteria,

viruses, parasites, and other antigens (Breslin et al. 2019). Several studies have

examined the impact of senescence on the GI tract immune functions. For example,

Mabbott et al. (2015) have shown that the human GI mucosal system is

compromised or morphologically changed with ageing, such as alterations in den-

dritic cell subsets, increased levels of tumor necrosis factor-α, reduced secretory IgA

levels, decreased natural killer cells, and phagocytic cell activity. They suggested

that immunosenescence contributes heavily to the increased risk of recurrent and

persistent infections in the elderly. The compromised immune system of the GI tract

can be further modified by immune-related comorbid conditions in frail and elderly

subjects (Maijo et al. 2014). Also, immunosuppression therapy can inhibit the GI

tract immune system in the elderly patients. A comprehensive review by Szalach

et al. (2019) reported that the plasma levels of pro-inflammatory cytokines and the

number of activated immune cells were very high in patients suffering from depres-

sion. The cytokine levels were markedly reduced in patients given antidepressant

therapy, suggesting the role of immune system in depression. It is assumed that

besides the nervous system, the GI tract’s immunocompetence may also be

modulated in patients receiving antidepressant drugs.

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