Method: 44 aging subjects will participate. The design is a 9 month, randomized, double-blind, placebo-controlled crossover study. Each subject will be "crossed over" between high dose Q10 (300mg), low dose Q10 (100mg), and placebo, receiving each agent for 3 month periods. Neither subjects nor investigators will know which substance each subject is receiving in which phase. Subjects will be randomly assigned to one of six arms.