The epidemiology of actinic keratosis varies throughout the world according to the genetic makeup and skin type of the population and their lifestyle habits, specifically time spent in the sun. The prevalence of the condition will be discussed in this article, in addition to the factors that impact the development of the skin lesions and prognosis.
The prevalence of actinic keratosis is highest in Australia, with an estimated prevalence of 37-55% in Australian adults over the age of 40. This is likely to be linked to the high UV radiation exposure to a population with relatively fair skin. Additionally, outdoor sports are very popular in Australian culture and, as a result, they tend to spend more time in the sun.
Comparably, the overall rate of actinic keratosis in the United States is estimated to be approximately 10.2% in females and 26.5% in males. In the United Kingdom, the prevalence is 15% in males and 6% in females.
In general, men are more likely than women to be affected by actinic keratosis, although this may be linked to other risk factors, such as the average time spent outside. Additionally, people with a high-fat diet also tend to have a higher risk of developing actinic keratosis, which is also more common in men.
Actinic keratosis most often affects individuals with white skin and is directly linked to cumulative exposure to UV radiation. As a result, the incidence of actinic keratosis is high for individuals who:
- Are elderly
- Live close to the equator
- Spend a lot of time outdoors (e.g. outdoor occupation or hobbies)
As the risk of actinic keratosis is linked to cumulative sun exposure, elderly individuals are most likely to be affected. There is a prevalence of approximately 10% in people aged between 20 and 30 years, whereas it is more than 90% in people over 80 years. In fact, some dermatologists believe all people eventually get actinic keratosis as they age.
Individuals most likely to be affected by actinic keratosis are those with fair skin. Ethnic groups with darker skin types are less likely to be affected and cases of actinic keratosis is rare in people with black skin.
Most patients with actinic keratosis have Fitzpatrick type I or type II skin, which are characterized by burning easily when exposed to UV radiation and the inability to tan. The prevalence of the condition declines during progression to Fitzpatrick skin types III, IV and V, until it becomes very rare in those with type VI skin. However, it should be noted that cutaneous malignancies might still affect individuals with dark skin, even if they are less likely to have actinic keratosis.
Prognosis and Rate of Progression
The prognosis of actinic keratosis is generally positive. With watchful waiting and treatment techniques, each of the skin patches can by treated individually, without the need for systemic treatment.
The exact rate of progression from actinic keratosis to squamous cell carcinoma is unclear and is likely to depend on several factors, such as the sun protection of the individual following diagnosis.
Preliminary research has indicated a risk of less than 1 in 1000 patches becoming cancerous each year. However, other research has suggested a much higher risk, closer to 1 in 10 cases. The exact rate is, therefore, unclear, although the connection is uncontested. The overall incidence of malignant and premalignant skin lesions, including actinic keratosis and other types, has increased from 3% to 8% since the 1960s.