Birthweight, vitamin D receptor gene polymorphism, and risk of lumbar spine osteoarthritis

Objective. To investigate risk factors for adult lumbar spine osteoarthritis (OA) including polymorphisms of the vitamin D receptor gene (VDR) and birthweight. Methods. Plain radiographs of the lumbar spine were taken in 392 healthy subjects and graded for osteophytes and disc space narrowing (DSN); demographic data were collected. Details of birthweight and weight at 1 year were retrieved from historical records. VDR gene allelic variation was analyzed in 291 subjects. Results. The mean age of the cohort was 65.8 years; mean weight was 68.9 kg in women and 80.1 kg and men. Osteophytes of grade >= 2 were found in 63.5% of this cohort; DSN >= 2 was present in 14.3% of subjects. Increasing osteophyte severity was significantly associated with age, adult weight, and manual social class; DSN was not. Presence and severity of osteophytes were associated with low birthweight and lower weight at 1 year in men, but not in women. No associations were found for DSN. The B allele of the VDR gene was associated with increasing severity of osteophyte. There was a significant interaction between birthweight and VDR gene in determining risk of osteophytosis in men (p for interaction = 0.04). The VDR-birthweight interaction pattern was similar but not statistically significant in women. Conclusion. Lumbar spine OA was a prevalent finding in this cohort. Both birthweight and polymorphisms in the VDR gene were associated with the presence of lumbar spine osteophytes and a significant interaction was observed between these 2 factors in men.