Abstract
Genome-wide alterations in RNA expression profiles are age-associated. Yet the rate and temporal pattern of those alterations are poorly understood. We investigated temporal changes in RNA expression profiles in blood from population-based studies using a quadratic regression model. Comparative analysis between two independent studies was carried out after sample-weighting that downsized differences in sample distribution over age between the datasets. We show that age-associated expression profiles are clustered into two major inclinations and transcriptional alternations occur predominantly from the seventh decade onwards. The age-associated genes in blood are enriched in functional groups of the translational machinery and the immune system. The results are highly consistent between the two population-based studies indicating that our analysis overcomes potential confounders in population-based studies. We suggest that the critical age when major transcriptional alterations occur could help understanding aging and disease risk during adulthood.