Sandra Freitag‐Wolf, Matthias Munz, Olaf Junge, Christian Graetz, Yvonne Jockel‐Schneider, Ingmar Staufenbiel, Corinna Bruckmann, Wolfgang Lieb, Andre Franke, Bruno G. Loos, Søren Jepsen, Henrik Dommisch, Arne S. Schaefer

• Aims Various studies have reported that young European women are more likely to develop early‐onset periodontitis compared to men. A potential explanation for the observed variations in sex and age of disease onset is the natural genetic variation within the autosomal genomes. We hypothesized that genotype‐by‐sex (G × S) interactions contribute to the increased prevalence and severity. Materials and methods Using the case‐only design, we tested for differences in genetic effects between men and women in 896 North‐West European early‐onsetAims Various studies have reported that young European women are more likely to develop early‐onset periodontitis compared to men. A potential explanation for the observed variations in sex and age of disease onset is the natural genetic variation within the autosomal genomes. We hypothesized that genotype‐by‐sex (G × S) interactions contribute to the increased prevalence and severity. Materials and methods Using the case‐only design, we tested for differences in genetic effects between men and women in 896 North‐West European early‐onset cases, using imputed genotypes from the OmniExpress genotyping array. Population‐representative 6823 controls were used to verify that the interacting variables G and S were uncorrelated in the general population. Results In total, 20 loci indicated G × S associations (P < 0.0005), 3 of which were previously suggested as risk genes for periodontitis (ABLIM2, CDH13, and NELL1). We also found independent G × S interactions of the related gene paralogs MACROD1/FLRT1 (chr11) and MACROD2/FLRT3 (chr20). G × S‐associated SNPs at CPEB4, CDH13, MACROD1, and MECOM were genome‐wide‐associated with heel bone mineral density (CPEB4, MECOM), waist‐to‐hip ratio (CPEB4, MACROD1), and blood pressure (CPEB4, CDH13). Conclusions Our results indicate that natural genetic variation affects the different heritability of periodontitis among sexes and suggest genes that contribute to inter‐sex phenotypic variation in early‐onset periodontitis.…