Multiple sclerosis and solar exposure before the age of 15 years: case-control study in Cuba, Martinique and Sicily

Association Between Time Spent Outdoors and Risk of Multiple Sclerosis

BACKGROUND AND OBJECTIVES

This study aims to determine the contributions of sun exposure and ultraviolet radiation (UVR) exposure to risk of pediatric-onset multiple sclerosis (MS).

METHODS

Children with MS and controls recruited from multiple centers in the United States were matched on sex and age. Multivariable conditional logistic regression was used to investigate the association of time spent outdoors daily in summer, use of sun protection, and ambient summer UVR dose in the year before birth and the year before diagnosis with MS risk, with adjustment for sex, age, race, birth season, child's skin color, mother's education, tobacco smoke exposure, being overweight, and Epstein-Barr virus infection.

RESULTS

Three hundred thirty-two children with MS (median disease duration 7.3 months) and 534 controls were included after matching on sex and age. In a fully adjusted model, compared to spending <30 minutes outdoors daily during the most recent summer, greater time spent outdoors was associated with a marked reduction in the odds of developing MS, with evidence of dose-response (30 minutes-1 hour: adjusted odds ratio [AOR] 0.48, 95% confidence interval [CI] 0.23-0.99, p = 0.05; 1-2 hours: AOR 0.19, 95% CI 0.09-0.40, p < 0.001). Higher summer ambient UVR dose was also protective for MS (AOR 0.76 per 1 kJ/m2, 95% CI 0.62-0.94, p = 0.01).

DISCUSSION

If this is a causal association, spending more time in the sun during summer may be strongly protective against developing pediatric MS, as well as residing in a sunnier location.

Matching participant address with public records database in a US national longitudinal cohort study

Background

Epidemiological studies utilize residential histories to assess environmental exposure risk. The validity from using commercially-sourced residential histories within national longitudinal studies remains unclear. Our study assessed predictors of non-agreement between baseline addresses from the commercially-sourced LexisNexis database and participants in the national longitudinal study, REasons for Geographic and Racial Differences in Stroke (REGARDS). Additionally, we assessed differences in stroke risk by neighborhood socioeconomic score (nSES) based on participant reported address compared to nSES from LexisNexis/REGARDS matched baseline address.

Methods

From January 2003–October 2007, REGARDS enrolled 30,239 black and white adults aged 45 and older within the continental United States and collected their baseline address. ArcGIS Desktop 10.5.1 with ESRI 2016 Business Analyst Data was used to geocode baseline addresses from LexisNexis and REGARDS. Logistic regression was used to estimate the likelihood that LexisNexis address matched REGARDS baseline address for each participant. Survival analysis was used to estimate association between nSES and incident stroke.

Results

Approximately 91% of REGARDS participants had a LexisNexis address. Of these geocoded addresses, 93% of REGARDS baseline addresses matched LexisNexis addresses. Odds of agreement between LexisNexis and REGARDS was higher for older-aged participants (OR = 1.02 per year, 95% CI: 1.01, 1.02), blacks compared to whites (OR = 1.16, 95% CI: 1.05, 1.29), females compared to males (OR = 1.15, 95% CI: 1.04, 1.26), participants with an income of $34k-74k compared to an income less than $20k (OR = 1.62, 95% CI: 1.39, 1.89). Odds of agreement were lower for residents in Midwest compared to residents in the south (OR = 0.82, 95% CI: 0.73, 0.94). No significant differences in nSES-stroke associations were observed between REGARDS only and LexisNexis/REGARDS matched addresses; however, differences in interactions were observed.

Conclusion

Agreement between LexisNexis and REGARDS addresses varied by sociodemographic groups, potentially introducing bias in studies reliant on LexisNexis alone for residential address data.

•

Approximately 9% of REGARDS participants did not have a LexisNexis address history available.

•

Of participants with both REGARDS and LexisNexis addresses available, 93% of these addresses matched.

•

Agreement between REGARDS and LexisNexis address varied by socio-demographics—potentially biasing environmental exposures.

•

Compared to LexisNexis, REGARDS addresses may be valuable in detecting interactions contributing to stroke disparities.

The effect of calcitriol and all-trans retinoic acid on T-bet, IFN-γ, GATA3 and IL-4 genes expression in experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is an immune-mediated inflammatory disease which affects the central nervous system (CNS). In the present study, the in vivo effects of ATRA, calcitriol, and their combinations on the expression of murine CD4+ T cell cytokines and their specific transcription factors in experimental autoimmune encephalomyelitis (EAE)-induced mice were explored. Thirty-two EAE induced inbred C57BL/6 female mice with an age ranged from 8 to 10 weeks were divided into four categories in a random manner. The first, second, and third groups received ATRA, calcitriol, ATRA+ calcitriol, respectively, and the fourth group received vehicle. The treatment started on the day prior to immunization and through the IP injections every other days for 21 days. The dosages of administration for calcitriol, ATRA, and calcitriol+ ATRA were 100 ng, 250 μg, and 50ng + 125 μg, respectively per mouse. An equal volume of excipient was administered for the vehicle group. T-bet, IFN-γ, GATA-3, and IL-4 genes expression were assessed in the splenocytes of EAE -induced mice. The expression of T-bet and IFN-γ genes in the splenocytes of ATRA, calcitriol and combination- treated mice were significantly reduced compared to vehicle group (p < 0.05). A significant decrease in T-bet expression was observed in the combination-treated group compared to the ATRA-treated group (p < 0.05). The expression of GATA3 and IL-4 genes was significantly increased in the ATRA-, calcitriol-, and combination-treated mice when compared with the control group (p < 0.05). Furthermore, the effect of calcitriol alone and in combination with ATRA was more considerable than that of ATRA alone. The nutraceutical approaches may be promising in the prevention and/or treatment of MS.

Skin Phototype Could Be a Risk Factor for Multiple Sclerosis

Environmental and genetic factors are assumed to be necessary for the development of multiple sclerosis (MS), however its interactions are still unclear. For this reason here, we have not only analyzed the impact on increased risk of MS of the best known factors (HLA-DRB1*15:01 allele, sun exposure, vitamin D levels, smoking habit), but we have included another factor (skin phototype) that has not been analyzed in depth until now. This study included 149 MS patients and 147 controls. A multivariate logistic regression (LR) model was carried out to determine the impact of each of the factors on the increased risk of MS. Receiver Operating Characteristics (ROC) analysis was performed to evaluate predictive value of the models. Our multifactorial LR model of susceptibility showed that females with light brown skin (LBS), smokers and who had HLA-DRB1*15:01 allele had a higher MS risk (LBS: OR = 5.90, IC95% = 2.39–15.45; smoker: OR = 4.52, IC95% = 2.69–7.72; presence of HLA-DRB1*15:01: OR = 2.39, IC95% = 1.30–4.50; female: OR = 1.88, IC95% = 1.08–3.30). This model had an acceptable discriminant value with an Area Under a Curve AUC of 0.76 (0.69–0.82). Our study indicates that MS risk is determined by complex interactions between sex, environmental factors, and genotype where the milieu could provide the enabling proinflammatory environment that drives an autoimmune attack against myelin by self-reactive lymphocytes.

Shedding light on the link between early life sun exposure and risk of multiple sclerosis: results from the EnvIMS Study

BACKGROUND

Lower levels of sun exposure in childhood have been suggested to be associated with increased risk of multiple sclerosis (MS). In this paper we extend previous work, using two novel analytical strategies.

METHODS

Data collected in the Environmental risk factors In MS (EnvIMS) study, a case-control study with MS cases and population-based controls from Canada, Italy and Norway, were used. Participants reported on sun exposure behaviours for 5-year age intervals from birth; we focused on the first three age intervals (≤15 years). We compared two life course epidemiology conceptual models, the critical period and the accumulation model. We also used latent class analysis to estimate MS risk for different latent sun exposure behaviour groups.

RESULTS

The analyses included 2251 cases and 4028 controls. The accumulation model was found to be the best model, which demonstrated a nearly 50% increased risk of MS comparing lowest reported summer sun exposure with highest [risk ratio (RR) = 1.47 (1.24, 1.74)]. The latent sun exposure behaviour group, characterized by low sun exposure during summer and winter and high sun protection use, had the highest risk of MS; a 76% increased risk as compared with the group with high sun exposure and low sun protection use [RR = 1.76 (1.27, 2.46)].

CONCLUSIONS

Our analyses provide novel insights into the link between sun exposure and MS. We demonstrate that more time indoors during childhood and early adolescence is linked with MS risk, and that sun protection behaviours in those who spend most time indoors may play a key role in increasing risk.

Environmental and genetic risk factors for MS: an integrated review

Recent findings have provided a molecular basis for the combined contributions of multifaceted risk factors for the onset of multiple sclerosis (MS). MS appears to start as a chronic dysregulation of immune homeostasis resulting from complex interactions between genetic predispositions, infectious exposures, and factors that lead to pro-inflammatory states, including smoking, obesity, and low sun exposure. This is supported by the discovery of gene-environment (GxE) interactions and epigenetic alterations triggered by environmental exposures in individuals with particular genetic make-ups. It is notable that several of these pro-inflammatory factors have not emerged as strong prognostic indicators. Biological processes at play during the relapsing phase of the disease may result from initial inflammatory-mediated injury, while risk factors for the later phase of MS, which is weighted toward neurodegeneration, are not yet well defined. This integrated review of current evidence guides recommendations for clinical practice and highlights research gaps.

Extra-Skeletal Effects of Vitamin D

The vitamin D receptor is expressed in multiple cells of the body (other than osteoblasts), including beta cells and cells involved in immune modulation (such as mononuclear cells, and activated T and B lymphocytes), and most organs in the body including the brain, heart, skin, gonads, prostate, breast, and gut. Consequently, the extra-skeletal impact of vitamin D deficiency has been an active area of research. While epidemiological and case-control studies have often suggested a link between vitamin D deficiency and conditions such as type 1 and type 2 diabetes, connective tissue disorders, inflammatory bowel disorders, chronic hepatitis, food allergies, asthma and respiratory infections, and cancer, interventional studies for the most part have failed to confirm a causative link. This review examines available evidence to date for the extra-skeletal effects of vitamin D deficiency, with a focus on randomized controlled trials and meta-analyses.

Benefits of Outdoor Sports for Society. A Systematic Literature Review and Reflections on Evidence

The combination of physical activity and being in nature is recognized as providing a range of significant benefits. The objective of this literature review was to compile an overview of the social benefits and costs associated with outdoor sports within the academic literature and to reflect on the quality of underlying evidence that supports the relationship. A systematic review was carried out with seven partners from different European countries, including Bulgaria, France, Germany, United Kingdom, Italy, Portugal, and Spain. From a total of 17,560 studies identified, 133 studies were selected with relevant data extracted to standardized forms. The selected studies have been analyzed with qualitative research methods. A meta-analysis could not be conducted due to the heterogeneity of the study designs and outcome measures. As a result, the review gives an overview of the social impacts associated with outdoor sports which have been clustered to six broad categories: physical health, mental health and wellbeing, education and lifelong learning, active citizenship, crime reduction, and anti-social behavior, as well as additional benefits. The review furthermore revealed gaps in the evidence base which are especially notable in the long-term effects that outdoor sports can have on personal and social development.

Outdoor physical activity bears multiple benefits to health and society

INTRODUCTION

Cutting-edge technologies and the rapid urbanization have led to several advantages for mankind and society. However such benefits have been accompanied with the alarming diffusion of sedentary lifestyle disorders, metabolic diseases, major depression and socialization problems, affecting global economy dramatically. The pandemic expansion of chronic diseases is associated with physical inactivity. During the last decade, numerous cities and organizations worldwide have started to adopt strategies aimed at improving outdoor physical activity levels in city residents.

EVIDENCE ACQUISITION

A systematic review focusing on the effects of regular outdoor sports and physical activities across all ages was conducted through multiple databases, according to the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) standards.

EVIDENCE SYNTHESIS

Performing outdoor sports and physical activities may bear social, psychological and physiological benefits. Preventive effects are similarly documented in youth and seniors towards several morbid conditions: vitamin D deficiency, multiple sclerosis, osteoporosis and myopia.

CONCLUSIONS

Giving the beneficial effects of outdoor sports and physical activities, promotion strategies should be strongly advocated and developed nationally and globally. Likewise, dedicated research areas should inspire guidelines for the promotion of various outdoor activities - a good practice for the social scenario and the healthcare system.

Are the protective benefits of vitamin D in neurodegenerative disease dependent on route of administration? A systematic review

Background: The clinical and preclinical exploration of the therapeutic properties of vitamin D have significantly increased in the past decade, owing to the growing associative evidence suggesting vitamin D is neuroprotective. However, whether depletion of vitamin D contributes to the onset of neurological disorders or is a symptom of neurological disease has yet to be defined. Much remains unclear about the causal role of vitamin D and the method of use and forms of vitamin D.Objectives: We sought to quantitatively assess if neuroprotective benefits from vitamin D in neurodegenerative diseases are dependent on route of administration: comparing the effect of endogenously sourced vitamin D from UV exposure to exogenously derived vitamin D through synthetic supplementation.Design: We systematically searched PubMed, Embase and PsycInfo databases which included both pre-clinical and clinical studies investigating vitamin D in neurodegenerative diseases. Articles were subject to strict inclusion criteria and objectively assessed for quality. Additionally, Medline data was analysed to identify trends in topic publications and linguistic characteristics of papers.Results: From a total of 231 screened articles, we identified 73 appropriate for review based on inclusion criteria: original studies that investigated vitamin D levels or levels of vitamin D supplementation in neurodegenerative diseases or investigated past/present sun exposure in disease cohorts. Results indicate there is insufficient evidence to comprehensively reflect on a potential neuroprotective role for vitamin D and if this was dependent on route of administration. The majority of current data supporting neuroprotective benefits from vitamin D are based on pre-clinical and observational studies. Solid evidence is lacking to support the current hypothesis that the beneficial effect of UV exposure results from the synthesis of vitamin D. Sun exposure, independent of vitamin D production, may be protective against multiple Sclerosis, Parkinson's disease and Alzheimer's disease. Yet, further research is required to elucidate the beneficial mechanism of actions of UV exposure. The literature of vitamin D and amyotrophic lateral sclerosis was limited, and no conclusions were drawn. Therefore, in cases where UV-derived vitamin D was hypothesized to be the beneficial mediator in the neuroprotective effects of sun exposure, we propose results are based only on associative evidence.Conclusion: On the basis of this systematic review, strong recommendations regarding therapeutic benefits of vitamin D in neurodegenerative disease cannot be made. It is unclear if vitamin D mediates a protective benefit in neurodegenerative disease or whether it is an associative marker of UV exposure, which may contribute to as of yet unidentified neuroprotective factors.

Incidence and Risk Profile of Dementia in the Regions of Middle East and North Africa

BACKGROUND

The risk of dementia is reported as "epidemic" and "looming" over the Middle East and North Africa (MENA) region. For this, we performed a multi-language review and feasible analysis on the incidence of dementia to offer apt conclusions.

METHODS

Totally, 3 databases (Magiran, Scientific Information Database, and PubMed) and 1 non-database source (Google) were searched in French, English, and Persian by using specific keywords and their combinations. All searches were independent and had no restriction for the year or type of publication. We also calculated cumulative incidence of dementia for Egypt and Israel-Palestine from relevant prevalence estimates by using standard formula.

RESULTS

Little information on incidence was available, sparing Israel (2.4/100,000/year; pre-senile). Ten (48.0%) countries had none-to-little information (of any kind) on dementia, indicating considerable awareness deficit in this region. Cumulative incidence of dementia in Egypt and Israel-Palestine was 2.7% over 20 years (55 new cases) and 14.7% (130 new cases) over 6 years, respectively. In Lebanon, cumulative incidence was 7.5% over 20 years. Data looked across dementia-related factors (i.e., fertility rate, polygamy, violence, hypovitaminosis D, diabetes, hypertension, life expectancy, age structure) did not seem to support epidemic proportions of dementia for MENA.

CONCLUSIONS

MENA is youthful and dementia here is neither likely to be an epidemic nor looming over. The only possible exception might be Arab pocket in Israel. To us, previous attributions on dementia do not seem to be based on the realities of this region and, therefore, may prevent pragmatic addressal of dementia. Lastly, values-based collaborations are invited to jointly fill the awareness deficit in a unique low-cost manner.

Vitamin D and Neurological Diseases: An Endocrine View

Vitamin D system comprises hormone precursors, active metabolites, carriers, enzymes, and receptors involved in genomic and non-genomic effects. In addition to classical bone-related effects, this system has also been shown to activate multiple molecular mediators and elicit many physiological functions. In vitro and in vivo studies have, in fact, increasingly focused on the "non-calcemic" actions of vitamin D, which are associated with the maintenance of glucose homeostasis, cardiovascular morbidity, autoimmunity, inflammation, and cancer. In parallel, growing evidence has recognized that a multimodal association links vitamin D system to brain development, functions and diseases. With vitamin D deficiency reaching epidemic proportions worldwide, there is now concern that optimal levels of vitamin D in the bloodstream are also necessary to preserve the neurological development and protect the adult brain. The aim of this review is to highlight the relationship between vitamin D and neurological diseases.

Factors associated with onset, relapses or progression in multiple sclerosis: A systematic review

Multiple sclerosis (MS) is a chronic disease of the central nervous system with an unidentified etiology. We systematically reviewed the literature on the possible risk factors associated with MS disease onset, relapses and progression from 1960 to 2012 by accessing six databases and including relevant systematic reviews, meta-analyses, case-control or cohort studies. The focus was on identifying modifiable risk factors. Fifteen systematic reviews and 169 original articles were quality assessed and integrated into a descriptive review. Best evidence, which included one or more prospective studies, suggested that lower exposure to sunlight and/or lower serum vitamin D levels were associated with an increased risk of developing MS onset and subsequent relapses, but a similar quality of evidence was lacking for disease progression. Prospective studies indicated that cigarette smoking may increase the risk of MS as well as accelerate disease progression, but whether smoking altered the risk of a relapse was largely unknown. Infections were implicated in both risk of developing MS and relapses, but data for progression were lacking. Specifically, exposure to the Epstein-Barr virus, particularly if this manifested as infectious mononucleosis during adolescence, was associated with increased MS risk. Upper respiratory tract infections were most commonly associated with an increase in relapses. Relapse rates typically dropped during pregnancy, but there was no strong evidence to suggest that pregnancy itself altered the risk of MS or affected long-term progression. Emerging research with the greatest potential to impact public health was the suggestion that obesity during adolescence may increase the risk of MS; if confirmed, this would be of major significance.

Use of Fingolimod in the Management of Relapsing-Remitting Multiple Sclerosis: Experience from Latin America

Once-daily fingolimod 0.5 mg (FTY720; Gilenya(®), Novartis Pharma AG, Basel, Switzerland) is a sphingosine 1-phosphate receptor modulator that is approved for the treatment of relapsing multiple sclerosis (MS); currently, this includes approval in 13 Latin American countries. However, despite a well-characterized efficacy and safety profile in a large clinical development program, thus far there has been limited representation of patients from across the Latin American region. Differences in MS disease characteristics have been reported for the Latin American population compared with Caucasians, which may be additional to recent improvements in MS diagnosis. Furthermore, healthcare provision and regional socioeconomic factors exist that are unique to Latin America compared with other regions. Therefore, to optimize MS treatment pathways and improve patient clinical outcomes, it is important to investigate the efficacy and safety profile of fingolimod using ethnically relevant data. Here, we review key data from Hispanic patients enrolled in the fingolimod clinical trial program, summarize recent findings from the FIRST LATAM study, and appraise fingolimod data from real-world patient populations.

FUNDING

Novartis Pharma AG, Basel, Switzerland.

The EnvIMS Study: Design and Methodology of an International Case-Control Study of Environmental Risk Factors in Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic disease of the central nervous system, often resulting in significant neurological disability. The causes of MS are not known; however, the incidence of MS is increasing, thereby suggesting that changes in lifestyle and/or environmental factors may be responsible. On this background, the Environmental Risk Factors in MS Study or EnvIMS study was designed to further explore the etiology of MS. The design and methodology are described, providing details to enable investigators to (i) use our experiences to design their own studies; (ii) take advantage of, and build on the methodological work completed for, the EnvIMS study; (iii) become aware of this data source that is available for use by the research community. Methods: EnvIMS is a multinational case-control study, enrolling 2,800 cases with MS and 5,012 population-based controls in Canada, Italy, Norway, Serbia and Sweden. The study was designed to investigate the most commonly implicated risk factors for MS etiology using a self-report questionnaire. Results/Conclusions: The use of a common methodology to study MS etiology across several countries enhances the comparability of results in different geographic regions and research settings, reduces the resources required for study design and enhances the opportunity for data harmonization.

Michel Dumas and Pierre-Marie Preux: promoting tropical neurology silently--the gist of their contributions

This article presents the contribution by two senior French Neurologists over the past three decades in building, developing and promoting 'tropical neurology' in a number of neglected countries of Asia, Africa and Latin America. It talks about the 'human, dedicational and contributive value' of these two experts who do not come from an English-speaking world. It highlights meaningful changes that have been achieved in different tropical countries as a result of their direct contribution. This overview may likely be a cause for learning and motivation to others to really work in and for tropical countries, where a large proportion of global health burden is to be found.

Can we prevent or treat multiple sclerosis by individualised vitamin D supply?

Apart from its principal role in bone metabolism and calcium homeostasis, vitamin D has been attributed additional effects including an immunomodulatory, anti-inflammatory, and possibly even neuroprotective capacity which implicates a possible role of vitamin D in autoimmune diseases like multiple sclerosis (MS). Indeed, several lines of evidence including epidemiologic, preclinical, and clinical data suggest that reduced vitamin D levels and/or dysregulation of vitamin D homeostasis is a risk factor for the development of multiple sclerosis on the one hand, and that vitamin D serum levels are inversely associated with disease activity and progression on the other hand. However, these data are not undisputable, and many questions regarding the preventive and therapeutic capacity of vitamin D in multiple sclerosis remain to be answered. In particular, available clinical data derived from interventional trials using vitamin D supplementation as a therapeutic approach in MS are inconclusive and partly contradictory. In this review, we summarise and critically evaluate the existing data on the possible link between vitamin D and multiple sclerosis in light of the crucial question whether optimization of vitamin D status may impact the risk and/or the course of multiple sclerosis.

Efficacy of vitamin D supplementation in multiple sclerosis (EVIDIMS Trial): study protocol for a randomized controlled trial

BACKGROUND

Multiple sclerosis is the most common chronic inflammatory disease of the central nervous system in young adults. Despite the fact that numerous lines of evidence link both the risk of disease development and the disease course to the serum level of 25-hydroxyvitamin D it still remains elusive whether multiple sclerosis patients benefit from boosting the serum level of 25-hydroxyvitamin D, mainly because interventional clinical trials that directly address the therapeutic effects of vitamin D in multiple sclerosis are sparse. We here present the protocol of an interventional clinical phase II study to test the hypothesis, that high-dose vitamin D supplementation of multiple sclerosis patients is safe and superior to low-dose supplementation with respect to beneficial therapeutic effects.

METHODS/DESIGN

The EVIDIMS trial is a German multi-center, stratified, randomized, controlled and double-blind clinical phase II pilot study. Eighty patients with the diagnosis of definite multiple sclerosis or clinically isolated syndrome who are on a stable immunomodulatory treatment with interferon-β1b will be randomized to additionally receive either high-dose (average daily dose 10.200 IU) or low-dose (average daily dose 200 IU) cholecalciferol for a total period of 18 months. The primary outcome measure is the number of new lesions detected on T2-weighted cranial MRI at 3 tesla. Secondary endpoints include additional magnetic resonance imaging and optical coherence tomography parameters for neuroinflammation and -degeneration, clinical parameters for disease activity, as well as cognition, fatigue, depression, and quality of life. Safety and tolerability of high-dose vitamin D supplementation are further outcome parameters.

DISCUSSION

In light of the discrepancy between existing epidemiological and preclinical data on the one hand and available clinical data on the other the EVIDIMS trial will substantially contribute to the evaluation of the efficacy of high-dose vitamin D supplementation in MS patients. The study design presented here fulfills the criteria of a high-quality clinical phase II trial in MS.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01440062.

The challenges of UV-induced immunomodulation for children's health

Exposure to solar ultraviolet radiation (UVR) is recognised to have both beneficial and harmful effects on human health. With regard to immune responses, it can lead to suppression of immunity and to the synthesis of vitamin D, a hormone that can alter both innate and adaptive immunity. The consequences in children of such UV-induced changes are considerable: first there are positive outcomes including protection against some photoallergic (for example polymorphic light eruption) and T cell-mediated autoimmune diseases (for example multiple sclerosis) and asthma, and secondly there are negative outcomes including an increased risk of skin cancer (squamous cell carcinoma, basal cell carcinoma and cutaneous malignant melanoma) and less effective control of several infectious diseases. Many uncertainties remain regarding the amount of sun exposure that would provide children with the most effective responses against the variety of immunological challenges that they are likely to experience.