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

• Published in: Osteoporosis international 2020-08, Vol.31 (8), p.1517-1524
• Main Authors: Thompson, M. J. W., Jones, G., Balogun, S., Aitken, D. A.
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; Bone Density; Cross-Sectional Studies; Endocrinology; Fractures, Bone - epidemiology; Fractures, Bone - etiology; Humans; Medicine; Medicine & Public Health; Melanin; Melanins - analysis; Middle Aged; Original Article; Orthopedics; Rheumatology; Risk Factors; Short term; Spectrophotometry; Spinal Fractures - epidemiology; Vertebrae; Vitamin D; Vitamin D3
• ISSN: 0937-941X; 1433-2965
• DOI: 10.1007/s00198-020-05304-4

Summary 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.