Can Sebum Reduction Predict Acne Outcome?
From The British Journal of Dermatology
Abstract
Sebum excretion has generally been accepted as an important factor in the development of acne vulgaris. However, the relationship of sebum excretion and acne outcome has not yet been clearly demonstrated quantitatively
The objective of this analysis was to explore the correlation of sebum and acne by combining data from studies of various acne treatments that have demonstrated effects on both sebum excretion and acne outcome. Acne measures included total lesion count, inflammatory lesion count and acne severity grade. For each acne measure, data were pooled and analysed at the 3- and 4-month endpoints, when sebum reduction has generally equilibrated and efficacy in acne is approaching the maximum effect for most treatments. A linear model was used to describe the percentage reduction in each acne measure as a function of percentage reduction in sebum excretion. Slope values were similar for the three acne parameters and all were significantly different from zero (P < 0·025), suggesting a significant correlation of sebum and acne. The projected sebum reduction required to achieve 50% reduction in acne measures ranged from 30% to 50%. The results shown here suggest that the collective data across multiple studies may provide a useful generalization of the association of sebum reduction and acne outcome. As the relationship apparently remains consistent regardless of the treatment, it can be inferred that extrapolation to novel exploratory treatments may be valid.
Introduction
Many researchers have observed that a correlation exists between sebum excretion and acne severity. In fact, this relationship has been clearly demonstrated in numerous studies over the past four decades. While the mechanism of acne lesion formation is multifactorial, sebum excretion plays an important role. Higher rates of sebum excretion are associated with more severe acne. Further, acne severity can be modulated by various medications that reduce sebum, and these parameters appear to be related at least in a qualitative fashion. We have attempted to look across multiple studies reported in the dermatology literature to determine if the sebum–acne relationship can be quantified and subsequently generalized to predict acne outcome from sebum reduction.
There are broadly two major classes of acne treatment that reduce sebum: systemic retinoids and hormones. The mechanisms of action by which these drugs improve acne are actually more complex, but they each reduce sebum secretion.
Retinoid therapy, specifically oral isotretinoin, provides the most effective acne treatment for moderate to severe inflammatory acne. However, because of its teratogenicity and adverse event profile, cautious use of this medication is required. Isotretinoin acts on multiple factors involved in acne pathogenesis, by normalizing follicular keratinization, indirectly inhibiting Propionibacterium acnes growth, decreasing inflammation, reducing sebaceous gland size and reducing sebum excretion. However, the exact mechanism(s) of action is not known. Among all acne medications, it has the greatest effect on sebum reduction reaching values of approximately 90%.[21] Interestingly, topical isotretinoin does not appear to affect sebum excretion and has only moderate efficacy in the treatment of acne.
While hormone therapy modulates sebum excretion to a lesser extent than systemic isotretinoin, it is an effective treatment for many women with acne. Several progestins, such as cyproterone acetate (CPA), demonstrate notable antiandrogenic properties and apparently have a direct effect on sebum excretion. Increased androgen activity, either systemic or local, is associated with sebaceous gland proliferation and elevated sebum excretion, and consequently has been linked to severity of acne. High doses of oestrogens are also linked to reduction in sebum production although the mechanism by which oestrogen affects sebum, apart from its antagonist effects on androgens, is not clear. With combination therapy of an oestrogen and CPA, sebum reduction of up to 75% has been reported.
The correlation of sebum and acne was explored across the spectrum of antiacne activity combining data from the various drug classes. Further, an attempt was made to model the relationship of sebum reduction with improvement in acne.
Abstract
Sebum excretion has generally been accepted as an important factor in the development of acne vulgaris. However, the relationship of sebum excretion and acne outcome has not yet been clearly demonstrated quantitatively