Daily Multivitamin Lowers Risk for Cataracts

Taking a multivitamin supplement daily may stave off development of cataracts in middle-aged and older men, according to an article published online November 21 in Ophthalmology. However, there appeared to be no association between daily vitamins and visually significant age-related macular degeneration (AMD).

William G. Christen, ScD, from the Division of Cardiovascular Disease, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, and colleagues analyzed results of the Physicians' Health Study (PHS) II, in which cataract and AMD were secondary endpoints. PHS II results for cardiovascular and cancer risk were published earlier.

The eye disease component of PHS II involved 11,497 male physicians randomly assigned to take a daily multivitamin (Centrum Silver, Pfizer) (n = 5736) or placebo (n = 5761) in the cataract part of the study, and 14,233 men randomly assigned to a multivitamin (n = 7111) or placebo (n = 7122) in the AMD part of the study. Study participants reported no cataract or AMD incidence at baseline.

The physicians completed annual questionnaires between 1997 and 2011 and provided information about pill-taking adherence, possible adverse events, risk factors, and occurrence of any new cataract or AMD cases. Researchers followed the participants for a mean of 11.2 years, confirming the occurrence of 1817 cataract and 1337 cataract extractions, along with 538 cases of AMD. Of the AMD cases, 281 were visually significant and 144 were advanced.

The researchers found a 9% lower risk for cataract among participants in the multivitamin group compared with the placebo group (hazard ratio [HR], 0.91; 95% confidence interval [CI], 0.83 - 0.99; P = .04). The benefit was greater in older men.

They found no statistically significant difference for visually significant AMD, although there was a trend for increased risk among the multivitamin group (152 vs 129 cases; HR, 1.19; 95% CI, 0.94 - 1.50; P = .15). However, the increased risk associated with vitamin use reached statistical significance when the investigators analyzed any type of AMD, with or without visual loss (294 vs 244 cases; HR, 1.22; 95% CI, 1.03 - 1.44; P = .02).

Small Percentage, Large Impact
"Cataract is a very common source of ocular morbidity in US adults. If our findings are real, that is, if multivitamins really do reduce the risk of cataract, even by a modest 10%, this rather small reduction would nonetheless have a large public health impact," Dr. Christen wrote.

Emily Y. Chew, MD, deputy clinical director at the National Eye Institute in Bethesda, Maryland, agrees. "It's akin to cardiovascular disease. Cardiovascular disease is very common, so even a 10% reduction is a huge relief of the burden of disease," she said. "Cataract is the most common surgery that Medicare pays for, and it's going to get worse. Anything we can do to reduce it is a major feat."

Dr. Chew was a leader in another prominent research project, Age-Related Eye Disease Study, or AREDS, which found similar results for multivitamin use. "We found that Centrum was protective for cataracts, just like they did here, but not for macular degeneration," she said. She is now a leader on the AREDS2.

The new data "at least suggests to the general clinician or the general ophthalmologist, maybe even the primary care physician, that the notion of taking a multivitamin is probably something that we should encourage in more patients than not," Matthew J. Welch, MD, a vitreoretinal surgeon at the Loyola University of Chicago Stritch School of Medicine in Maywood, Illinois, said. "You're probably doing yourself some good — you're definitely not doing yourself any harm — by taking a multivitamin, and maybe that does stave off your cataract progression."

Why Not AMD?
Researchers still have to tease out why no significant benefit was shown for AMD in PHS II.

"A true lack of effect is one possibility," Dr. Christen said. "Another possibility is that our finding of no significant benefit or harm may simply be due to the play of chance. Other possibilities include inadequate dosages or inadequate follow-time. It may also be that a different combination of nutrients is required."

The newly published results differ from the results of AREDS, in which participants taking high-dose antioxidant combination of vitamin C, vitamin E, β-carotene, and zinc showed a slower progression to AMD. But in PHS II, the doses were only recommended daily allowances, and AREDS participants were higher-risk individuals.

One issue with the PHS II study, according to Dr. Welch, is that it was designed primarily for finding cardiovascular and cancer risks and that it was based on self-reported information from physicians.

"You're dealing with a group of individuals that view their time as highly valuable and aren't necessarily going to be running to the doctor every time they notice something," he explained. "I think probably if this had been designed specifically to evaluate the eye, they may have found more of a difference [for AMD]. There may be more cataracts and AMD found if individuals were systematically screened."

Dr. Welch said he thinks unknown benefits from dietary supplements probably exist: "It's just that it's hard to tease out. It's not as easy as it is in a drug trial."