ReviewRisks and benefits of UV radiation in older people: More of a friend than a foe?
Introduction
Public health and advisory bodies currently advise that sun exposure (UV radiation) should be limited based on the associated adverse effects of which the most important is the development of skin cancer [1].
The risks from excessive UV exposure are well established but benefits on several markers of health are also emerging, in addition to the main effect of cutaneous vitamin D synthesis. The association between vitamin D deficiency and a number of serious non-skeletal conditions is well described in the literature. It is unclear if vitamin D itself is responsible for all these relationships or is a surrogate marker of UV exposure, and other mechanisms are implicated. Biological effects of UV separate to Vitamin D photosynthesis are now being explored due to the apparent reduction in all cause mortality in populations with increased UV exposure.
The mortality and morbidity associated with hypertension and vascular disease in the older population far exceeds that of skin cancer and we will review the hypotheses pertaining to the role of UV in blood pressure modulation, cardiovascular disease and stroke.
There is significant variation in UV exposure dependent on latitude and environmental factors. Sun exposure advice should thus be tailored to local ambient conditions and geographical location.
The objectives of this review are to explore the evidence for the harm and benefit of UV exposure in the older adult population. Some of these benefits will be vitamin D related but we also explore the benefits that may be independent of vitamin D levels.
Pubmed, Medline, Embase, Cinahl and The Cochrane Databases were searched. No date or language restrictions were placed on the articles origins. Bibliographies from papers were also analysed for additional relevant publications.
All the articles were obtained and evaluated for relevance. Only those with the most relevance were used in this review. Key search words used in combination were: Ultraviolet Rays, Ultraviolet, UV, UV radiation, sunlight, sunlight exposure, old age, elderly, geriatric, aged, Benefit and harm. Finally, 50 articles were selected for inclusion.
Ultraviolet or solar radiation can be categorised according to its wavelength into UVA, UVB and UVC Figure 1. Sunlight is predominantly comprised of UVA – 90% and UVB – 10%. Less than 2.5% of the sun's radiation permeates through the earth's atmosphere and UVC is absorbed before reaching the Earth's surface [2]. Incident UV at the Earth's surface varies due to changes in atmospheric absorption, time of day, latitude, altitude, cloud cover and season.
Biological activity is wavelength dependant with UVA penetrating deeper into the dermis whilst UVB is largely absorbed within the epidermis. These wavelength differences determine the location and type of biological activity. Excessive exposure results in acute keratinocyte damage, apoptosis and mutation to p53 suppressor genes. UVA damages DNA indirectly through free radical formation and oxidative injury, while UVB radiation causes direct DNA damage with signature mutations predisposing to skin cancers. Other biological effects of UV include photo ageing, inflammation and burning in addition to Vitamin D synthesis [3].
Section snippets
Risk versus benefit
Policies strictly limiting sun exposure are now being challenged in older adults [4]. 20% of the UK population aged > 65 years cannot recall the last episode of any form of outdoor exercise [5] and vitamin D deficiency in the older population is widespread [6].
Skin cancers
The global incidence of skin cancer continues to rise. The commonest cutaneous cancers can be subdivided into Malignant Melanoma (MM) and Non Melanoma Skin Cancer (NMSC).
Conclusions
Further scrutiny and study are required regarding the potential benefits of UV radiation based on plausible mechanisms of benefit in addition to harm particularly in the elderly.
There is a need to review recommendations of sun avoidance as this may be to the detriment not only of vitamin D synthesis but also of more relevant health endpoints such as reduced all cause mortality, hip fractures, blood pressure and vascular events.
Older adults should adopt a balanced approach to sun exposure.
Contributors and their role
Wright-Weller statements. Dr Weller had the initial idea for this review, edited it, and is its guarantor. Dr Wright wrote the first draft of the manuscript. The authors declare that they have no conflicts of interest. The authors declare no sources of funding for this review article.
Competing interests
None declared.
Provenance and peer review
Commissioned and externally peer reviewed.
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