Skin Photosensitivity is Associated with 25-Hydroxyvitamin D and BMD but not Fractures Independent of Melanin Density in Older Caucasian Adults.

Whether skin photosensitivity modulates sun exposure behaviours, consequent vitamin D status and skeletal health outcomes independently of constitutive pigmentation have not been systematically investigated. 1072 community-dwelling adults aged 50-80 years had skin photosensitivity quantified by questionnaire and melanin density by spectrophotometry. Bone mineral density (BMD), falls risk and 25-hydroxyvitamin D (25OHD) were measured using DXA, short form physiological profile assessment and radioimmunoassay, respectively. Sun exposure and symptomatic fractures were assessed by questionnaire. Participants were followed up at 2.5 (n = 879), 5 (n = 767) and 10 (n = 571) years. Higher resistance to sunburn and greater ability to tan were associated with reduced sun protection behaviours (RR 0.87, p < 0.001 & RR 0.88, p < 0.001), higher lifetime discretionary sun exposure in summer (RR 1.05, p = 0.001 & RR 1.07, p = 0.001) and winter (RR 1.07, p = 0.001 & RR 1.08, p = 0.02) and fewer lifetime sunburns (RR 0.86, p < 0.001 & RR 0.91, p = 0.001). Higher resistance to sunburn was associated with lower total body (ß = - 0.006, p = 0.047) and femoral neck (ß = - 0.006, p = 0.038) BMD, but paradoxically, fewer prevalent fractures (RR 0.94, p = 0.042). Greater ability to tan was associated with higher 25OHD (ß = 1.43, p = 0.04), lumbar spine (ß = 0.014, p = 0.046) and total body (ß = 0.013, p = 0.006) BMD, but not fracture or falls risk. These associations were independent of constitutive melanin density. Cutaneous photosensitivity was associated with sun exposure behaviours, cutaneous sequelae and, consequently, 25OHD and BMD in older Caucasian adults independent of constitutive melanin density. There was no consistent association with fracture outcomes, suggesting environmental factors are at least as important.

Constitutive melanin density is associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults.

Higher cutaneous melanin reduces vitamin D3 production. This may increase fracture risk. We found that cutaneous melanin density was associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults. Melanin density either acts as a surrogate marker or its relationship with fracture changes with time. INTRODUCTION: Higher cutaneous melanin reduces vitamin D3 production. This may impact lifetime vitamin D status and increase fracture risk. This study aimed to describe the relationship between spectrophotometrically determined constitutive melanin density, prevalent and incident fractures in a cohort of exclusively older Caucasian adults. METHODS: 1072 community-dwelling adults aged 50-80 years had constitutive melanin density quantified using spectrophotometry. Participants were followed up at 2.5 (n = 879), 5 (n = 767), and 10 (n = 571) years after the baseline assessment. Prevalence and number of symptomatic fractures were assessed by questionnaire. RESULTS: Higher melanin density was independently associated with greater prevalence of any fracture (RR 1.08, p = 0.03), vertebral fracture (RR 1.41, p = 0.04) and major fracture (RR 1.12, p = 0.04) and the number of fractures (RR 1.09, p = 0.04) and vertebral fractures (RR 1.47, p = 0.04) in cross-sectional analysis. At the 2.5-year follow-up, higher melanin density was associated with incident fractures (RR 1.42, p = 0.01) and major fractures (RR 1.81, p = 0.01) and the number of incident fractures (RR 1.39, p = 0.02) and major fractures (RR 2.14, p = 0.01). The relationship between melanin density and incident fracture attenuated as the duration of follow-up increased and was not significant at the 5- or 10-year follow-up. CONCLUSIONS: Constitutive melanin density was associated with prevalent and short-term, but not long-term, incident fracture risk in older Caucasian adults. This suggests melanin density either acts as a surrogate marker for an unmeasured fracture risk factor or the relationship between melanin density and fracture changes with time.

Constitutive melanin density is associated with higher 25-hydroxyvitamin D and potentially total body BMD in older Caucasian adults via increased sun tolerance and exposure.

Greater skin pigmentation reduces dose equivalent cutaneous vitamin D3 production, potentially impacting lifetime vitamin D status and fracture risk. We show that melanin density was positively associated with 25-hydroxyvitamin D and total body bone mineral density. These relationships were partially explained by greater sun exposure due to more permissive skin phenotype. INTRODUCTION: Higher cutaneous melanin reduces vitamin D3 production. This may impact lifetime vitamin D status and increase fracture risk. This study aimed to describe the relationship between spectrophotometrically determined constitutive melanin density, osteoporotic risk factors and potential intermediaries in a cohort of exclusively older Caucasian adults. METHODS: One thousand seventy-two community-dwelling adults aged 50-80 years had constitutive melanin density quantified using spectrophotometry. Sun exposure, skin phenotype, non-melanoma skin cancer (NMSC) prevalence and smoking status were assessed by questionnaire. Bone mineral density (BMD), falls risk, physical activity and 25-hydroxyvitamin D were measured using DXA, the short form Physiological Profile Assessment, pedometer and radioimmunoassay, respectively. RESULTS: Higher melanin density was independently associated with greater ability to tan (RR = 1.27, p < 0.001), less propensity to sunburn (RR = 0.92, p < 0.001), fewer lifetime sunburns (RR = 0.94, p = 0.01), current smoking (RR = 1.41, p < 0.001), female sex (RR = 1.24, p < 0.001) and less photodamage (RR = 0.98, p = 0.01). The associations between melanin density and sun exposure (RR = 1.05-1.11, p < 0.001-0.01), sun protection behaviours (RR = 0.89, p < 0.001) and NMSC prevalence (RR = 0.75, p = 0.001) were no longer significant after taking into account skin phenotype and sun exposure, respectively. 25-Hydroxyvitamin D was strongly associated with higher melanin density (ß = 1.71-2.05, p = 0.001). The association between melanin density and total body BMD (ß = 0.007, p = 0.04) became non-significant after adjustment for 25-hydroxyvitamin D. There was no association between melanin density and physical activity, falls risk or BMD at other sites. CONCLUSIONS: Our data support a model of higher constitutive melanin density underpinning a less photosensitive skin phenotype, permitting greater sun exposure with fewer sequelae and yielding higher 25-hydroxyvitamin D and, potentially, total body BMD.

The relationship between cumulative lifetime ultraviolet radiation exposure, bone mineral density, falls risk and fractures in older adults.

Data linking cumulative lifetime vitamin D status with skeletal outcomes are lacking. We show that increasing cumulative sun exposure was associated with higher bone mineral density in younger males and protective against fractures in females independent of current vitamin D. This supports the concept that cumulative sun exposure is an important contributor to skeletal health. INTRODUCTION: While low 25-hydroxyvitamin D levels are associated with increased fracture risk, this reflects only recent sun exposure. The Beagley-Gibson (BG) method utilises microtopographical skin changes to quantify cumulative lifetime ultraviolet radiation (sun) exposure. This study aimed to describe the relationship between BG grade, BMD, falls risk and fractures in older adults. METHODS: Eight hundred thirty-five community-dwelling adults aged 53-83 years had silicone casts from the dorsum of both hands graded by the BG method. BMD was measured using DXA and falls risk using the short form of the Physiological Profile Assessment. Vertebral deformities and symptomatic fractures were assessed by DXA and questionnaire, respectively. RESULTS: The relationship between BG grade, spine BMD and vertebral fracture varied depending upon sex. In females, increasing grade was associated with lower vertebral fracture prevalence (OR = 0.44/grade, p = 0.018) and fewer fractures (OR = 0.82/grade, p = 0.021), particularly major fractures (OR = 0.75/grade, p = 0.03). In males, increasing grade was associated with more DXA-detected vertebral deformities (RR = 1.28/grade, p = 0.001), but not symptomatic fractures. These relationships were independent of BMD, falls risk, smoking and current 25-hydroxyvitamin D. BG grade was not associated with falls risk. For BMD, there were interactions between BG grade and both age and sex and a positive trend with hip BMD in younger males. CONCLUSIONS: BG grade demonstrated beneficial associations with fracture outcomes in females and BMD in younger males independent of current 25-hydroxyvitamin D. These data support the concept that cumulative ultraviolet radiation exposure is an important determinant of skeletal health. The association with vertebral deformities in males may reflect outdoor physical trauma in younger life.

Predictors of Beagley-Gibson skin cast grade in older adults.

BACKGROUND AND PURPOSE: The Beagley-Gibson (BG) grading system utilizes microtopographical skin changes to generate an individualized, objective estimate of cumulative, lifetime ultraviolet radiation (UVR) exposure. However, predictors of BG grade are ill-defined, particularly in older populations. The aim of this cross-sectional study was to describe the factors associated with skin damage as measured by the BG method in 835 community-dwelling older adults. METHODS: Study participants aged 53-83 years had silicone casts taken from the dorsum of both hands and graded by the BG method. Lifetime sun exposure, skin phenotypic traits and smoking status were assessed by questionnaire. 25-hydroxyvitamin D and melanin density were measured using radioimmunoassay and spectrophotometry, respectively. Ordered logistic regression was used to compute a single odds ratio (OR) by taking BG grade as the outcome variable. RESULTS: Higher 25-hydroxyvitamin D was associated with increasing BG grade (OR = 1.39, P = 0.02) in adjusted analysis. Age (OR = 1.14, P < 0.001), occupational sun exposure (OR = 1.62, P < 0.001), ability to tan (OR = 1.40, P < 0.001), melanin density (OR=0.79, P = 0.001), lifetime leisure time sun exposure (OR = 1.21, P = 0.004), current smoking (OR = 1.82, P = 0.007), propensity to sunburn (OR = 1.18, P = 0.016), and waist-hip ratio (OR = 1.10, P = 0.02) were independent predictors of BG grade. Hair colour, number of sunburns, body mass index and gender were not independent predictors of BG grade. CONCLUSIONS: Beagley-Gibson skin cast grade is a biologically relevant marker of UVR exposure in older adults influenced by both intrinsic and extrinsic factors.