Aging Skin: Causes and Treatment

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by

Torunn Sivesind, M.D.

 

Introduction

Skin aging is a common concern and represents a very broad topic. The term “skin aging” is used to describe the changes occurring in the elasticity,  structure, and tone of the skin over time. The manifestations of skin aging are many, including increased wrinkling, sagging, thinning, sun spots, dryness, and prolonged healing from wounds or injury. These changes can be the result of “physiological” aging — which can be thought of as the normal or natural alterations occurring within the skin over the years — or can be due to a kind of accelerated or premature aging caused by environmental exposures such as ultraviolet rays from the sun or tanning beds, cigarette smoking, or simply the effect of gravity. The types of skin aging are therefore classically thought of as two distinct types:

 

The normal, physiological, or “intrinsic” type of skin aging is controlled mainly by genetics — how we are programmed to age, and how quickly these changes appear. Intrinsic aging is largely unavoidable

 

“Extrinsic” aging is due to environmental and lifestyle factors such as excessive exposure to ultraviolet light. Some of these extrinsic factors can be minimized or mitigated. Extrinsic aging accelerates the normal aging process, with loss of the normal skin architecture, increased inflammation, and damage to DNA

 

Mechanisms of Aging

To understand why the skin appears differently with the passage of time, it helps to understand the basic structure of the skin and how this structure changes over time. The skin consists of three main layers: the outermost layer is called the epidermis and is responsible for skin tone and waterproofing; under the epidermis lies the dermis, where the hair follicles and sweat glands are located; and deeper still lies the hypodermis (also called the subcutaneous fat layer), which is made of connective tissue and fat. As the skin ages, the epidermal layer thins, likely due to flattening of its natural ridged pattern that provides fullness. The dermal and subcutaneous layers likewise thin, and the region where the epidermis meets the dermis becomes flatter, impeding the transfer of vital nutrients needed for healthy skin.

 

The lowermost cells of the epidermal layer, called basal cells, are constantly replicating (dividing into new cells), moving upward toward the surface, and replenishing this outermost skin layer. However, as the skin ages, these basal cells lose their ability to replicate. The cells that cannot regenerate anymore are known as “senescent” cells, meaning they cannot grow or divide into new cells anymore. These senescent cells accumulate over time.

 

While the skin itself ages, so too do the underlying structures, such as muscles and bones. The muscles that underlie and support the skin become atrophied, permanently over contracting as a compensatory mechanism, which causes “dynamic” wrinkles (wrinkles that appear with movement) to appear. Fat tissue can become ptotic  (drooped) and undergo atrophy, leading to a loss of fullness and youthful curves. Skeletal changes also occur and are particularly noticeable in the face. The skeletal support system undergoes bony tissue resorption, occurring preferentially in particular areas of the facial skeleton, and this results in profound changes in the appearance of facial soft tissue. This preferential bone resorption means that the regions of the face — the upper, middle, and lower thirds of the face – do not age symmetrically and must be treated differently due to different underlying changes.

 

Causes of Aging Skin

The skin acts as a kind of protective garment; a covering that protects the internal organs and serves as a first line defense against the external environment. Scientists are studying the factors that lead to senescence and the mechanism of senescence itself in order to find ways to slow the process. The mechanisms underlying the physiological aging process are not fully understood, though research indicates that the physiological aging process, including senescence, is affected by cellular stressors, such as reactive oxygen species (ROS, discussed later). Other important changes seen in aging skin cells include the shortening of telomeres (the ends of DNA strands, which act as a sort of buffer to protect the important information coded by DNA), or more simply by a cell coming to the end of its ability to undergo another sequence of replication (replicative  senescence).

 

The environmental and lifestyle-related causes of aging that comprise the extrinsic causes of skin aging include tobacco smoke, exposure to sun or tanning beds, air pollution (including smog, particulates, ozone, and others), squinting or other repeated facial expressions, the effect of gravity, dietary factors such as sugar and simple carbohydrate consumption, alcohol consumption (dehydrates the skin), and skin irritation (as from aggressive scrubbing or cleansers, or even from sweat that is not washed off promptly). We can limit or prevent some of these extrinsic factors that cause skin to appear older.

 

The mechanisms involved in extrinsic skin aging are now better-understood by scientists, who continue to conduct research to enable better prevention of extrinsic aging. Photodamage, the skin damage caused by exposure to the sun’s ultraviolet (UV) light, specifically from UVB rays (in the spectrum of 290-320 nm) and UVA rays (comprising the 320-400 nm range), includes skin cancer as well as the less-serious signs of aging. Photoaging is the most understood and well-documented type of extrinsic aging which manifests as wrinkles, permanent pigmentary changes (age/sun spots), pre-cancers, and skin cancer.

 

Recently, it has also been discovered that the visible ranges of light (400-700 nm) and infrared light (over 800 nm) also contribute damaging effects to the skin. Atmospheric exposure, as from air pollution, seems to initiate a cascade of reactions within the skin, started when reactive oxygen species ( ROS) are created. These ROS cause a specific type of damage to cells, called oxidative stress or oxidative damage, whereby cellular constituents like proteins, fats, and the genetic components (DNA and RNA) are injured. These damaged cells then undergo an inflammatory response, which causes further damage to the skin.

 

Prevention

Since photoaging is a major cause of premature skin aging and skin cancer, limiting one’s sun exposure, using broad spectrum sunscreens with an SPF of 30, or higher, and avoiding tanning beds are all effective measures one can take to reduce the extrinsic causes of skin aging. Topical antioxidant preparations can be used to protect the skin from oxidative stress caused by atmospheric pollutants. Recent clinical studies have shown that topical antioxidant regimens can mitigate the harmful effects of air pollution. Positive results of such regimens may be seen with the naked eye and include improvement in skin tone, reduction in wrinkling, skin roughness, and discoloration. Additionally, when viewed microscopically, skin cells protected by a topical antioxidant show preservation of normal structure and function, with fewer signs of damage when compared to placebo.

 

Treatment

Treatments for aging skin range from noninvasive topical agents to extensive surgical procedures. New treatment options are emerging rapidly. Often, treatment of aging skin includes a combination approach such as the use of topical products and medications, along with resurfacing procedures, injectables, and surgical interventions in order to achieve an ideal result.

 

The simplest and least invasive treatments for aging skin are topical agents, which are applied directly to the skin’s surface. Topical preparations such as retinoids ( Retin-A)  contain scientifically-proven bioactive ingredients that act to improve the skin’s appearance through a variety of mechanisms, which may include increased cellular signaling via growth factors, neutralizing free radicals, reducing the breakdown of elastin and collagen, or activating stem cells.

 

Skin resurfacing treatments – which include chemical peels, microneedling, and lasers — are minimally invasive treatments to repair skin damage and reduce the visible signs of aging.  Microneedling is a type of purposeful injury to the dermis that triggers a healing cascade within the skin, characterized by increased collagen synthesis. Recovery is speedy, with little to no downtime and minimal side effects. It can be used to treat wrinkles and reduce scarring from acne or other causes

 

Chemical peels involve the application of chemical agents   ( acids) to the skin, causing controlled destruction of part (or all) of the epidermis and dermis. These layers are ablated and undergo exfoliation. After exfoliation, the wounded skin undergoes a healing cascade of remodeling and rejuvenation, with increased collagen synthesis and improved texture and appearance of the skin. Chemical peels are classified by how deeply they penetrate the skin and are referred to as superficial, medium, or deep.

 

Lasers come in many different types, though the most commonly used are the CO2 and erbium:YAG types, which are known as ablative lasers, meaning they remove the top layer of skin and promote new collagen synthesis. These ablative lasers are ideal for treating more severe photodamage and wrinkling, particularly in those with lighter skin types.

 

Today, there are also non-ablative lasers, which deliver heat to the dermis without harming the overlying skin, and are more gentle than ablative lasers (though not as effective for severe skin damage).  There are also fractional types of both the ablative and non-ablative lasers, which better distribute the effects of the laser, but require more treatments for maximal results. Non-ablative and fractional lasers can provide good results with less downtime and risks, and can be ideal for younger patients. Intense Pulsed Light (IPL) is yet another light based treatment which has demonstrated success in reducing hyperpigmentation (brown pigment in the skin) and redness from dilated blood vessels.

 

Injectable agents are increasingly popular and come in two main varieties, dermal fillers and neuromodulators. Dermal fillers are made of hyaluronic acid derivatives   ( Restylane and others), calcium hydroxyapetite ( Radiesse), or poly-L-lactic acid ( Sculptra), which are strategically injected to temporarily reduce the appearance of creases and lines, to plump tissues such as the lips, and fill hollows or depressed scars.

 

Neuromodulators, such as BOTOX Cosmetic, are injectable forms of the bacterial toxin known as botulinum toxin, which are used to temporarily correct muscle induced skin wrinkling or creasing and to improve facial dyssymmetry and reshape the face. These work by temporarily inhibiting the nerve signals that cause muscles to contract, thereby diminishing wrinkles that occur with movement. Early and consistent use of neuromodulators may also be preventive against signs of aging

 

Finally, there are surgical interventions for aging skin. For the aging face, these procedures include lifts for the brows, eyelids, nose, and midface, and chin augmentation, as well as the face lift and “thread lift,” which uses sutures to suspend the tissues of the face so that it appears lifted and more youthful.

 

Conclusion

While skin aging is a natural and physiological process, the prevention and mitigation of premature skin aging from environmental and lifestyle factors is possible, and there are a multitude of treatment options available to improve the quality and appearance of aging skin. Talking with a dermatologist or a plastic surgeon can help clarify the available options and enable decision making to formulate the best plan for achieving one’s desired results.

 

 

References

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