These results from PHS II hint at some benefit, but recommending supplements would be premature.
Oxidative stress has been implicated in the development of cognitive decline and dementia. Several studies have assessed whether antioxidant vitamins can lower the risk for cognitive decline, and results have been mixed. Researchers from the Physicians’ Health Study (PHS) II, an extension of the original PHS, assessed whether participants randomized to receive beta carotene (50 mg on alternate days) had a lower risk for cognitive decline than placebo recipients. Participants included 4052 male physicians enrolled in the original PHS and 1904 new recruits. Because cognition was added to the PHS as an ancillary study, it was not measured at baseline but only near the close of the beta carotene arm, which ended in 2003.
Among new recruits, who took study agents for only 1 year, no effect on cognitive function was detected across study arms. However, among original participants, who received the agents for a mean of 18 years, the beta carotene group had a better mean global score of cognitive function than the placebo group; the difference was statistically significant, but modest.
Comment: Only one other randomized trial of antioxidant supplementation (with vitamin E) has shown benefit in reducing cognitive decline. Other studies have failed to show benefit, and some have detected potential harm. However, this trial is the first to extend beyond 10 years, and the effect of antioxidants may be discernable only with long-term therapy. Nonetheless, I agree with the editorialist that the modest treatment effect seen in this trial is insufficient to warrant recommending beta carotene supplementation to our patients.
Jamaluddin Moloo, MD, MPH
Published in Journal Watch General Medicine November 29, 2007
Citation(s):
Grodstein F et al. A randomized trial of beta carotene supplementation and cognitive function in men: The Physicians’ Health Study II. Arch Intern Med 2007 Nov 12; 167:2184.
