First investigation of two obesity-related loci (TMEM18, FTO) concerning their association with educational level as well as income: The MONICA/KORA study

Background: Strong evidence exists for an association between socioeconomic status and body mass index (BMI) as well as between genetic variants and BMI. The association of genetic variants with socioeconomic status has not yet been investigated. The aim of this study was to investigate two obesity-related loci-the transmembrane 18 (TMEM18) and the fat mass and obesity-associated (FTO) gene-for their association with educational level and per capita income, and to test whether the detected genotype-BMI association is mediated by these social factors. Methods 12 425 adults from a large population-based study were genotyped for the polymorphism rs6548238 near TMEM18 and rs9935401 within the FTO gene. Data on educational level and per capita income were based on standardised questionnaires. Results High educational level and high per capita income were significantly associated with decreased BMI (-1.503 kg/m ₂, p<0.0001/-0.820 kg/m ₂, p<0.0001). Neither the polymorphism rs6548238 nor rs9935401 nor their combination were significantly associated with educational level (p=0.773/p=0.827/p=0.755) or income (p=0.751/p=0.991/p=0.820). Adjustment for social factors did not change the association between rs6548238 or rs9935401 and BMI. Conclusions: As far as the authors know, this is the first study to investigate the association between polymorphisms and socioeconomic status. The polymorphisms rs6548238 and rs9935401 showed no association with educational level or income.