Like it or not, the face reveals our age which is why people spend so much time and money trying to hide or reverse the tell-tale signs. It is not just the skin that is affected, other structures too are affected which combined together produce the signs we commonly associate with ageing. To help you understand what happens to the face, it is useful to think of the face as a three-layered structure consisting of:-

• The foundation or the bony skeleton and cartilage.
• The support system or the muscles of facial expression. The muscles of the face have fibrous insertions in the skin so that we can express happiness, sadness, anger and so on. They also support the eyebrows, eyelids, and the corners of the mouth.
• The outer covering or the skin. Normally, the skin is flexible and elastic. It can be pulled, depressed or creased but always returns to its original shape.

Ageing affects all three layers. The foundation decreases in volume and this is particularly noticeable on the lower third of the face due to loss of teeth and alveolar resorption (alveolar tissue supports the teeth) and shrinkage of the jaw bone.Combined with a receding hairline, this results in the upper and middle third of the face appearing disproportionately long compared to the lower third. If the outer covering or skin is elastic it will still spring back against the foundation even if the latter is reduced in volume. Unfortunately, the skin also loses elasticity with age. This results in an excess of skin which sags under the effect of gravity or muscular action leading to deep wrinkles and creases along the expression lines of the face. There is also loss of the support system due to muscle weakness which results in sagging eyebrows and eyelids, eyebags, jowls, downward migration of the nose and down-turning of the corners of the mouth.

The ageing skin - its 10% genes and 90% sun-damage

In the past, doctors thought that skin ageing was an inevitable and wrinkles, sagging skin and age spots were regarded as part of the normal ageing process over which we had little or no control. They were wrong because research has shown that the main factor responsible for up to 90% of skin ageing is cummulative exposure to the sun, the other 10% being due to genetic factors. Skin ageing is now thought to occur in two ways - through the natural ageing process which dermatologists call chronological ageing (also known as chronoageing, natural ageing, intrinsic ageing or biological ageing) and through sunlight accelerating the ageing process which doctors call photoageing (also called extrinsic ageing or dermatoheliosis). Chronological ageing is genetically determined and can only be controlled to a small extent, through healthy habits and lifestyles. Photoageing, on the other hand, is sun-induced ageing which is almost 100% preventable.

The term cummulative means that the damage accumulates a little at a time with each exposure, often unnoticed, until many years later. If you get a wrinkle in the thirties or forties, it is not a result of the last weekends' day out in the sun but the sum total of all the past exposures to the sun. The damage has already been done which means that the signs of sun-damage will continue to develop even if you start avoiding the sun from this day on. This is why it is important to take precautions early, preferably from childhood. Attitudes need to changed from one that regards a tan as being healthy to one that regards a tan as indicating sun-damage to the skin. Remember, the cosmetic consequence of sun-exposure is premature ageing - sagging, wrinkled and unevenly coloured skin but the medical consequence is even worse - increased risk of skin cancer.

There are differences in gross and microscopic appearance between chronologically aged skin and photoaged skin. Briefly, chronologically aged skin is thinned and finely wrinkled because everything slows down with age whereas in photoageing, the skin is metabolically more active, presumably to repair the damage and to protect the skin against further trauma.

The rate of cell renewal slows down by about 30 - 50% between the ages of 30 and 80 years. This means that the old stratum corneum cells on the surface of the skin are not replaced as quickly as they should be. These cells are less well cemented together so the skin becomes dry and flaky. The production of natural moisturising factors (NMFs) and sebum also decreases with age, further contributing to the dryness. Melanocytes and the blood vessels in the upper dermis are also reduced, accounting for the paleness of the aged skin. The epidermis is also thinned by about 20% by the age of 70 years and there is loss of the rete ridges (the downward indentations of the epidermis that anchor the epidermis to the dermis below). This results in a decreased adherence of the epidermis to the dermis so the aged skin is more susceptible to tearing and blister formation. However, despite all these changes, the epidermal cells appear normal unlike in photoaged skin (see below). Langerhan cells, the specialised immune cells that detect abnormal proteins and process and then pass them on the other cells of the immune system are also reduced in number - there are 15% fewer Langerhan cells in the buttock skin of people aged 65 years or more compared to those aged 24 years or less. This may be one reason why cancers are more common in the elderly. The melanocytes are not only reduced in number but also in efficiency. The elderly skin is therefore, less able to tan and less able to protect itself from sun-damage. This is why, even though sun-damage has been sustained during earlier years, it is still important to protect the skin against sun-damage in the elderly.

The dermis underneath is also thinned due to loss of connective tissue, fluid and mucopolysaccharides. The molecular structure of the collagen is altered so that the fibres do not interlock with each other as well as normal collagen, resulting in loss of firmness. The elastin fibres are also more irregular in arrangement and looser in texture, resulting in loss of elasticity and skin recoil. Therefore, instead of the extensible skin which can be pulled and pushed and yet returns to normal, the skin becomes lax and folded. The muscles also weaken with age. A weakening of the orbicularis oculi muscle around the eyes, for example, allows fat to herniate through resulting in bags under the eyes. The eyebrows may sag due to a weakening of the frontalis (forehead) muscle and jowls may form at the angles of the jaw due to a weakening of the platysma neck muscle. Fat is reduced, resulting in loss of fullness and sunken cheeks.

Earlier on we learnt that in chronological ageing, everything slows down. In photoageing however, the reverse is true because the skin has to work harder (cell renewal rate is actually increased) to repair the damage and protect itself. The stratum corneum layer is increased as a result of this and this results in an increase in the amount of keratin which helps to shield off some UV rays (60% of UV-B and 20% of UV-A). The skin also becomes tanned as the number and activity of the melanocytes (pigment-producing cells) increase to protect the skin against further sun-damage. These melanocytes, however, are working beyond capacity such that their efficiency eventually declines resulting in too much pigment being produced in some areas (causing age spots or solar lentigines) and too little in others (causing idiopathic guttate hypomelanosis - the reverse of age spots). Because of rapid cell renewal rate and the direct effect of UV rays on deoxyribose nucleic acid or DNA (the cell’s genetic blueprint), abnormal cells are produced, which if unchecked, can develop into solar keratoses (skin precancers) and eventually, skin cancers. The number of Langerhan cells which help to detect abnormal proteins are even more markedly reduced in number compared with chronologically aged skin and this may be one of the reasons why cancers develop on sun-exposed skin.

Skin through the decades of life

We will know that we will grow old eventually but how are you faring at the moment? Is your skin good or bad for your age? To help you answer this question, here's a diary of how our skin changes as we age.

If these changes sound all too familiar, don't feel despondent because modern medicine has a lot to offer. It is not much fun looking old but if you could look better for your age, just imagine what a boost that will give to your self-esteem. Naturally, if the changes are already severe, more drastic treatments will be necessary. This is why early treatment is recommended. Refer also to the section on wrinkles in Skin A to Z.

The female hormone, oestrogen stimulates the production of the hyaluronic acid, one of the main water-attracting substances found in the dermis and may also retard the decrease in collagen that occurs with age. This may be one reason for the dryness and loss of skin firmness after the menopause. Hormone replacement therapy (HRT) after the menopause may help to retard this so it is discussing the pros and cons of this with your gynaecologist.