Elsevier

Maturitas

Volume 81, Issue 4, August 2015, Pages 425-431
Maturitas

Review
Risks and benefits of UV radiation in older people: More of a friend than a foe?

https://doi.org/10.1016/j.maturitas.2015.05.003Get rights and content

Highlights

  • Excess ultraviolet exposure is a risk factor for skin cancer development.

  • There are no data showing an increase in all-cause mortality with high sun exposure.

  • Sunlight exposure has several health benefits dependently and independently of vitamin D synthesis.

  • UV exposure may lower blood pressure by a skin nitric oxide dependent pathway.

  • ‘Healthy sun exposure’ needs to be calculated based on beneficial as well as detrimental effects.

Abstract

Incident ultraviolet radiation from sunlight varies in intensity and spectrum with season and latitude and has both deleterious and beneficial effects on health in older people. Sunlight is the major preventable risk factor for skin cancer. Non-melanoma skin cancer is the commonest malignancy in a pale skinned older population, but the mortality is extremely low. Intermittent sun exposure is a risk factor for the more dangerous melanoma but chronic sun exposure and outdoor occupation may be protective. Public health advice has tended to concentrate on the dangers of sun exposure despite the absence of any data that increased sun exposure correlates with raised all-cause mortality.

Inadequate sun exposure carries its own risks, and the older population are particularly sun deprived as recorded by low serum Vitamin D levels and lack of outdoor activity. Sunlight has health benefits dependently and independently of vitamin D synthesis. Low serum vitamin D levels correlate with increased morbidity and mortality but the direction of association is not always clear. Vitamin D has a causal role in calcium and phosphate metabolism, in skeletal health and probably reduction of colorectal cancer. Evidence is weak for a role in cardiovascular health, but mobilisation of nitric oxide by UVA radiation from nitrate stores in skin, with consequent reduction in BP, may account for the observed reduction in cardiovascular disease and all-cause mortality with increased sun exposure. Advice on healthy sun exposure needs to be reconsidered, with reduction in all-cause mortality and morbidity as the primary end point.

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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