Ageing and the Special Senses

Original Editor - User Name

Top Contributors - Lucinda hampton, Kim Jackson, Simisola Ajeyalemi, Rucha Gadgil, Tolulope Adeniji and Aminat Abolade  

Introduction

The special senses are the senses that have specialized organs devoted to them. Special senses include the following:

• Hearing and balance (which includes the auditory system and vestibular system)
• Sight/Vision (the eye)
• Smell (the nose)
• Taste (the tongue)

We experience the environment around us through our senses. Neurones relay this information, via the central nervous system, to the brain. If the central nervous system or the brain deteriorate, as a result of age or illness then this flow of sensory information can also deteriorate.

• As we age the level of stimulation required to make the brain aware of a sensation also rises (effectively reducing the sensitivity of our senses).
• A healthy lifestyle, a healthy environment and seeking medical advice when needed can go some way towards helping protect the senses.

Changes to the Sensory System

As we age, our sensory functions decline contributing to an increased isolation from the outside world, forcing us to adopt perceptual aids (e.g., glasses, hearing aids). This has been demonstrated especially for hearing and vision. Older people usually experience a decline in visual acuity because of changes in lens elasticity which consequently lead to a decrease in abilities to focus on near objects (i.e., presbyopia) and to adapt to light. Also hearing is well known to decline with age and is usually characterized by a decreased hearing sensitivity, capability to understand speech in a noisy environment, slowed central processing of acoustic stimuli, and impaired sound localization. It has been estimated that about 30% of men and 20% of women in Europe have a hearing loss of 30dB or more at the age of 70 years old. Similarly, deficits in smell and taste are highly prevalent in older people from approximately 60 years of age.

Impaired sensory functioning impacts the quality of life of older people by influencing the way they experience the environment and react to stimuli and limiting social activities (may lead to isolation and depression). Sensory deficiency has also negative consequences for somatic health. eg. vision loss increases the risk of falls and fractures; olfactory loss complicates the detection of dangers in the environment (e.g., smoke, gas, spoiled food).

Eyesight In the Elderly, refer to link

Hearing in the Elderly, refer to link

Effects of Ageing on Smell and Taste

1.Taste

Gustatory dysfunction may be related to the normal ageing process.

• In many cases, what is perceived as a taste defect is truly a primary defect in olfaction (smell).
• Other than smell dysfunction, the most frequent causes of taste dysfunction are prior upper respiratory infection, head injury, drug use, and idiopathic causes. 
• Chewing problems associated with tooth loss and dentures can also interfere with taste sensations, along with the reduction in saliva production. Rather than whole mouth tastse dysfunction, regional deficits are much more common. It has been reported that there is a higher prevalence of localised losses on the tongue in elderly subjects than in young subjects. Despite their wide prevalence, most elderly people are unaware of regional taste deficits.

People who have taste disorders may benefit from flavour enhancement of their foods. Flavour enhancers supplement, enhance, or modify the original taste or aroma of a food but do not have a characteristic taste or aroma of their own.eg Salt, monosodium glutamate. Flavour enhancement for the elderly and sick can improve food palatability and acceptance, increase lymphocyte counts, improve grip strength, reverse or slow functional decline, and improve overall quality of life. It also has the potential to compensate for anorexia.

2. Smell

• Both the number of fibres in the olfactory bulb, along with olfactory receptors decrease noticeably with age. The bulb losses are secondary to sensory cell loss in the olfactory mucosa, along with a general deterioration in central nervous system cognitive processing functions. Olfactory receptor neurones undergo apoptosis at a baseline rate in each person (we have the ability to replace these cells, however this process degenerates with ageing).
• Another contributing factor when considering age related olfactory deterioration is mild cognitive impairment and Alzheimer's disease. Electrophysiological results of patients with Alzheimer's disease and pre‐clinical Alzheimer's disease confirm olfactory dysfunction.

Once diminished smell is diagnosed, the goal of management entails preventing injury related to this. Visual stimulating gas detection devices are good for those with a gas stove, as the person may not be able to smell gas leaks. Relatives or neighbours need closer involvement to check for spoiled food that if eaten could lead to food poisoning. 

Treatment

Confusional states can be caused by sensory deprivation or communication may be affected.

It is important to talk more slowly and clearly than loudly.

Check hearing aids are working correctly, and keep a communicator at hand, but be ready to use written communication methods or basic sign language. If repetition of a sentence is necessary, initially do not change the order of the words you used; it may be that person may not have heard you fully, rather than because they have misunderstood what you have said.

Resources

Ageing and the Central Nervous System: Special Senses