Acne Distribution
Although adolescent acne is the commonest form of the condition, acne may affect anyone from a baby through to an adult. Similarly, the anatomical distribution of acne on the body varies considerably between the different clinical types of acne. Knowledge of the usual distribution of the types of acne on the body and across different age groups may help sufferers identify if they have an unusual form of the condition which requires specialist medical attention.
Prevalence of Acne
Information about the distribution of acne is obtained by studying very large groups of people, selected because they are representative of the 'normal population' in terms of their age, sex and ethnic origin. Prevalence figures provide no information as to the likelihood of an individual developing acne One could examine each member of the group and determine how many of them had acne, from which the prevalence of acne in the general population could be calculated. Prevalence is like a snapshot, it tells you how many people have the acne at a particular point in time, usually expressed in terms of number of cases per 1,000 of population. Information about the prevalence of acne in the population, and in particular age groups, is useful for people planning healthcare services, since it predicts how many people will have acne and might require treatment at any particular time. However, the prevalence of acne provides no information as to the likelihood of an individual member of the population developing acne.
Incidence of Acne
Instead of examining the group only once to determine the prevalence of acne, you could study the group over a prolonged period of time. This would enable you to count the number of people who developed acne during the course of the study, from which you can calculate the incidence of acne in population. The incidence of acne is the number of new cases of acne occurring in a given period of time, the figure usually expressed in terms of number of cases per 1,000 population per year. Again, you could calculate the incidence of acne not just for the whole population, but for particular age groups. Age related acne incidence figures are of much more interest to individuals, as they represent the 'odds' of someone in that age range developing acne within a particular period of time. Incidence figures also help doctors decide whether acne is to be expected in patients of a particular age or represents an unusual occurrence worthy of investigation.
Predisposing Factors For Acne
Returning to the group who develop acne, selected from the larger study population, you might be able to find features which were more common in your group of acne sufferers than in the population as a whole. Things that make it more likely that a person will develop acne are called predisposing factors You might, for example, find that there were more overweight people and more males in acne group than in the general population. It would be wrong in this case to conclude that being male causes acne, as clearly there will also be females in the group who have developed acne and males in the group which has not, but it may indicate being male makes it more likely that the person will develop acne. Factors which make it more likely that a person will develop acne, but do not of themselves cause acne, are known as predisposing factors for acne. Predisposing factors for acne may be intrinsic and unalterable, such as a person's age, sex or ethic origin or they may be capable of being modified to reduce the likelihood of developing ace, such as a person's diet or weight.
Anatomical Distribution of Acne
Acne can develop on skin covering any area of the body, except the palms of the hands, the soles of the feet, the lips and the genital and oral mucosae. The distribution of spots on the body of a person affected by acne may provide an indication of the clinical type of acne and the cause. The sections which follow describe the typical pattern of distribution of acne over the face, back, chest, genitals and other body parts in the different clinical types of acne.
