Study to prove the benefits of using Sunscreen and Prevention of Skin Ageing

Study to prove the benefits of using Sunscreen and Prevention of Skin Ageing .

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Ann Intern Med. 2013;158(11):I-28. doi:10.7326/0003-4819-158-11-201306040-00001

What is the problem and what is known about it so far?

Changes in the appearance of the skin are known to be influenced by sun exposure and the effects of growing older. Although sunscreen has been shown to protect against skin cancer, whether it can protect against skin aging has not been established. Antioxidants, such as β-carotene, have also been suggested to protect against skin aging, but this has not been well-studied.

Why did the researchers do this particular study?

To find out whether daily sunscreen and β-carotene each protect against skin aging.

How was the study done?

Patients who were younger than 55 years were randomly assigned to a group asked to apply sun-protection factor 15+ sunscreen to their head, neck, arms, and hands each morning and after bathing, after spending more than a few hours in the sun, or after sweating heavily or to a group asked to use sunscreen at their discretion. Participants were also randomly assigned to receive daily β-carotene or placebo pills. Impressions were taken of the backs of participants’ hands at the beginning of the study and 4.5 years later. The impressions were examined for microscopic changes of skin aging by assessors who did not know to which study groups the participants had been assigned.

What did the researchers find?

More participants assigned to daily sunscreen use reported applying sunscreen at least 3 to 4 days each week than did participants in the discretionary-use group. Those in the daily-use group were less likely to have increased skin aging after 4.5 years than were those in the discretionary-use group. No difference in aging was seen between persons who received β-carotene pills and those who received placebo pills.

What were the limitations of the study?

About one third of participants did not have impressions of their skin taken at both the beginning and end of the study; although this did not seem to affect the results, an effect on the findings cannot be conclusively ruled out. The study was too small to confidently conclude a true lack of effect of β-carotene, and a larger or longer study might show a modest benefit or some harm of β-carotene use on skin aging. How these results would apply to people older than 55 years is not certain.

What are the implications of the study?

Daily use of sunscreen seems to protect against skin ageing.

Item 1 of 1    (Display the citation in PubMed)

1. J Am Acad Dermatol. 2008 May;58(5 Suppl 2):S149-54. doi: 10.1016/j.jaad.2007.04.035.
Broad-spectrum sunscreens provide better protection from solar ultraviolet-simulated radiation and natural sunlight-induced immunosuppression in human beings.
Moyal DD1, Fourtanier AM.
Author information:
•  1L'Oréal Recherche, Clichy, France. dmoyal@rd.loreal.com
Abstract
BACKGROUND: 
It is well established that ultraviolet (UV) radiation induces immunomodulatory effects that may be involved in skin cancer. Recent studies have shown that UVA (320-400 nm) and UVB (290-320 nm) radiation are immunosuppressive. As a result, sunscreens, which mainly absorb UVB, may be less effective in preventing UV radiation-induced immunosuppression than broad-spectrum products.
OBJECTIVE:
We sought to study the effects of UVA exposure on human delayed-type hypersensitivity (DTH) response and compare the efficacy of sunscreens having different levels of sun-protection factor (SPF) and UVA protection against both solar-simulated radiation and outdoor real-life sunlight exposure conditions.
METHODS: 
DTH was assessed using a kit which includes 7 recall antigens that most of the participants encountered during childhood immunization. Evaluation of DTH test response was made 48 hours after test application before and after UV exposure with or without sunscreens.
RESULTS:
In unprotected participants, the response to DTH tests was significantly reduced irrespective of UV types of exposure (full-spectrum UVA, long UVA, solar-simulated radiation). A UVB sunscreen failed to protect from solar-simulated radiation-induced immunosuppression. In contrast, a broad-spectrum sunscreen with the same SPF but providing a high protection in the UVA range significantly reduced local UV-induced immunosuppression and prevented the distant effects. In the outdoor study, as compared with DTH responses obtained before sun exposure, no alteration of immune response was detected when the skin was protected by a broad-spectrum sunscreen having a high protection level in the UVA (SPF 25, UVA protection factor 14). Conversely a broad-spectrum sunscreen with lower protection against UVA (SPF 25, UVA protection factor 6) failed to prevent UV-impaired response.
LIMITATIONS: 
These results have been obtained after repeated exposure. Additional experiments obtained under acute exposure are in progress.
CONCLUSION:
These findings clearly demonstrated the role of UVA in the induction of photoimmunosuppression together with the need for sunscreen products providing efficient photoprotection throughout the entire UV spectrum.
PMID: 18410801 [PubMed - indexed for MEDLINE]