Osteoporosis and Solar Irradiance

Osteoporosis and UV

Osteoporosis is a progressive bone disease that is characterised by a decrease in bone mass and density, which can lead to an increased risk of fracture. Osteoporosis is common in the UK with three million sufferers and 300,000 people receiving treatment from the NHS each year for fragility fractures i.e. those occurring from a fall from standing height or less. A lack of vitamin D is associated with osteoporosis, individuals with levels of 25-hydroxy vitamin D below 30 nmol/l are at greatest risk, although some individuals between 30-50 nmol/l may also be insuffucient.This is significant given that approximately 47% of Britons have levels below 40 nmol/l during winter and spring and 15% during summer and autumn. Vitamin D is obtained through sun exposure and to a much lesser extent from dietary sources, but it can also be supplied pharmaceutically

The UK Biobank provides an excellent opportunity to understand the determinants of osteoporosis due to the large number of incident fracture cases (e.g. 3,000 hip fracture cases by 2017), quantitative ultrasound measures of the heel, dual energy X-ray absorptiometry at multiple sites and extensive phenotypic information. Existing ultraviolet radiation (UVR) datasets from JAXA Satellite Monitoring for Environmental Studies (JAXA/EORC/JASMES) were utilised, with linkage facilitated by the MEDMI project, and merged with information on residential location, sun behaviours and dietary habits.The researchers investigated the complex interaction between modifiable factors responsible for osteoporosis.

The researchers hypothesised that lifetime UVB was inversely associated with osteoporosis risk and positively associated with skin cancer. Key effect modifiers, such as pharmaceutical use of vitamin D, were investigated to inform on which individuals may benefit most from specific guidelines.

There is potential to apply similar methods to extra-skeletal diseases, with which vitamin D has been associated previously.