Association between adiposity and facial aging: results from a Mendelian randomization study

BackgroundSkin, as a sociologically meaningful interface, has psychological implications different from other organs, particularly in the context of the global population aging. Growing evidence suggests that facial aging is associated with an increased risk of adiposity. Existing research, however, were observational, and while they may find some correlations, it is difficult to simply disentangle non-causal or reverse-causal links because these associations may be confounded or fail to accurately reflect true causative linkages.ObjectivesWe conducted a 2-sample Mendelian randomization (MR) study to examine the potential effect of facial aging on the risk of broad obesity and its three major adiposity indicators, including body mass index (BMI), body fat percentage (BF%) and waist circumference (WC).MethodsGenetic instruments from IEU OpenGWAS project, one of the largest available genome-wide association studies (GWAS) for facial aging (423,999 samples) were used to investigate the relation to broad obesity (32,858 cases, 65,839 controls). Using the inverse-variance weighted (IVW) technique, single nucleotide polymorphisms (SNPs) associated with adiposity indicators (BMI (461,460 samples), BF% (454,633 samples), and WC (462,166 samples)) were investigated in relationship to facial aging. Further sensitivity analyses were performed, including Mendelian randomization-Egger (MR-Egger), weighted median estimates, and leave-one-out analysis, to evaluate the consistency of the results and related potential issues in MR studies.ResultsWe identified strong and significant correlations between adiposity and facial aging in the 17 broad obesity-associated SNPs (IVW estimate of odds ratio OR = 1.020, 95% CI 1.010-1.029, P = 7.303e - 05), 458 BMI-associated SNPs (IVW estimate of odds ratio OR = 1.047, 95% CI 1.0357-1.058, P = 1.154e - 16),for the 395 BF%-associated SNPs (OR = 1.056, 95%CI 1.040-1.072,P = 7.617e - 12), or for the 374 WC-associated SNPs (OR = 1.072, 95% CI 1057-1.087,P = 1.229e - 23). A range of complementary methodologies have been employed to evaluate horizontal pleiotropy and related potential caveats occurring in MR research.ConclusionsUsing Mendelian randomization as an alternative approach to investigate causality, we found a causal relationship between adiposity and facial aging, which was statistically strong and significant. Using a two-sample Mendelian randomization, we found a causal relationship between adiposity (and its three major adiposity indicators, including body mass index, body fat percentage and waist circumference) and facial aging, which was statistically strong and significant.Among the three adiposity indicators, WC had a better casual association with facial aging, which indicated that subcutaneous fat may present a major contribution in facial aging compared with visceral fat.More detailed causal relationship was revealed in negative results of subsequent multivariable MR analysis (three major adiposity indicators with facial aging) and two sample MR analysis between visceral/subcutaneous adipose tissue and facial aging.

Automated summary

Facial aging has a causal relationship with adiposity and its three major indicators, including body mass index, body fat percentage, and waist circumference. This relationship was found through a two-sample Mendelian randomization study and was statistically strong and significant. Waist circumference showed a stronger causal association with facial aging compared to the other two indicators.