Gene-environment interaction between body mass index and transforming growth factor beta 1 (TGFbeta1) gene in knee and hip osteoarthritis

INTRODUCTION: The objective was to investigate potential gene-environment interaction between body mass index (BMI) and each of eight TGFbeta1 polymorphisms in knee and hip osteoarthritis (OA). METHODS: We conducted a case-control study of Caucasian men and women aged 45-86 years from Nottingham, United Kingdom (Genetics of OA and Lifestyle [GOAL] study). Cases had clinically severe symptoms and radiographic knee or hip OA; controls had no symptoms and no radiographic knee/hip OA. We used logistic regression to investigate the association of TGFbeta1 polymorphisms and OA when stratifying by BMI. Knee and hip OA were analyzed separately with adjustment for potential confounders. Additive and multiplicative interactions were examined. RESULTS: 2048 cases (1042 knee OA, 1006 hip OA) and 967 controls were studied. For hip OA, the highest risk was in overweight (BMI[greater than or equal to]25kg/m2) individuals with the variant allele of single-nucleotide polymorphism (SNP) rs1800468 (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.55-3.15). Evaluation of gene-environment interaction indicated significant synergetic interaction (relative excess risk due to interaction [RERI]=0.93, synergy index [SI]=4.33) with an attributable proportion due to interaction (AP) of 42% (AP=0.42; 95%CI 0.16-0.68). Multiplicative interaction was also significant (OR for interaction [ORINT]=2.27, p=0.015). For knee OA, the highest risk was in overweight individuals with homozygous genotype 11 of SNP rs2278422 (OR=6.95, p