Higher levels of vitamin D are associated with an increased risk of hip replacement for osteoarthritis but only in men, Australian researchers report.

The study of 9135 participants from the AusDiab study found that in males a one-standard-deviation increase in 25-hydroxy-vitamin D was associated with a 25% increased incidence of hip replacement.

A dose response relationship was evident by quartiles of 25-hydroxy-vitamin D concentration, reported the researchers led by Flavia Cicuttini from Monash University in Melbourne.

The association remained after adjusting for age, body mass index, ethnicity, smoking status, physical activity, season of blood collection, latitude, hypertension and diabetes, and area level disadvantage, they reported in Osteoarthritis and Cartilage.

Mechanisms for the link were unclear but could include the importance of vitamin D in regulating calcium homeostasis and formation of bone, a link with BMD or the fact that participants with the highest levels were more active which could contribute to wear and tear, the study authors said.

Reasons for the lack of association in females was also unclear, but it was possible that differences in vitamin D levels observed between genders may influence other biochemical or hormonal measures related to bone and cartilage health.

There were some limitations to the study, the authors noted, including the fact that participants were not investigated at baseline for hip OA.

“Serum 25(OH)D may be a marker of OA incidence, progression, or a marker of being selected for  arthroplasty,” they suggested.

“Our study adds to the ongoing debate regarding the optimal serum concentrations of vitamin D for skeletal health particularly in the setting of widespread vitamin D supplementation,” they concluded.