 A total of 506 men and women will be randomized to receive either 1 vitamin B supplementation consisting of folic acid 5mg, vitamin B12 0.4mg, and vitamin B6 50mg, or 2 a matching placebo. Participants will receive ultrasonography at baseline and every 6 months for 2.5 to 4.5 years, and CT scan at baseline and end of study 2.5 to 4.5 years. 