BACKGROUND: This study evaluates whether specific patterns of interleukin (IL)-1 gene variants, known to affect periodontitis severity, influence the previously reported association between obesity and subsequent periodontitis progression in a longitudinal database. The study population included 292 men (aged 29 to 64 years at entry) from the Veterans Affairs Dental Longitudinal Study from whom DNA and dental and anthropometric endpoints were collected during multiple examinations (approximately every 3 years for up to 27 years). METHODS: Key variables assessed included: 1) periodontitis; 2) body mass index; 3) waist circumference to height (WHTR) ratio for central adiposity; 4) age; 5) smoking; 6) glucose tolerance; and 7) two previously reported versions of IL-1 genetic patterns associated with periodontitis severity and progression. Disease progression was determined using predefined criteria that used a combination of change in classification of disease severity based on alveolar bone loss and tooth loss during follow-up. Extended Cox regression analyses were used to estimate hazards of experiencing periodontal disease progression with or without adjustments for appropriate covariates. RESULTS: In hazard ratio analyses, men with WHTR >50% at baseline and positive for either IL-1 genotype version were at significantly higher risk (two-fold) for disease progression (P for interaction = 0.04). Participants positive for IL-1 genotype version 2 exhibited earlier progression (fewer years from baseline to first incidence of progression) than those who were negative (P = 0.02, adjusted for age and smoking). CONCLUSION: In this longitudinally monitored male population, observed effect of baseline central adiposity on future periodontitis progression is conditional on proinflammatory IL-1 genetic variations.
BACKGROUND: This study evaluates whether specific patterns of interleukin (IL)-1 gene variants, known to affect periodontitis severity, influence the previously reported association between obesity and subsequent periodontitis progression in a longitudinal database. The study population included 292 men (aged 29 to 64 years at entry) from the Veterans Affairs Dental Longitudinal Study from whom DNA and dental and anthropometric endpoints were collected during multiple examinations (approximately every 3 years for up to 27 years). METHODS: Key variables assessed included: 1) periodontitis; 2) body mass index; 3) waist circumference to height (WHTR) ratio for central adiposity; 4) age; 5) smoking; 6) glucose tolerance; and 7) two previously reported versions of IL-1 genetic patterns associated with periodontitis severity and progression. Disease progression was determined using predefined criteria that used a combination of change in classification of disease severity based on alveolar bone loss and tooth loss during follow-up. Extended Cox regression analyses were used to estimate hazards of experiencing periodontal disease progression with or without adjustments for appropriate covariates. RESULTS: In hazard ratio analyses, men with WHTR >50% at baseline and positive for either IL-1 genotype version were at significantly higher risk (two-fold) for disease progression (P for interaction = 0.04). Participants positive for IL-1 genotype version 2 exhibited earlier progression (fewer years from baseline to first incidence of progression) than those who were negative (P = 0.02, adjusted for age and smoking). CONCLUSION: In this longitudinally monitored male population, observed effect of baseline central adiposity on future periodontitis progression is conditional on proinflammatory IL-1 genetic variations.