In addition, older individuals are likely to have taken calcium supplements for a longer duration with potentially cumulative adverse effects. Calcium plays an important role in neuronal cell regulation and function. Not surprisingly, changes in normal calcium homeostasis can lead to permanent neurologic damage, and excessive levels of calcium trigger caspase-dependent cell death.

Given previously described pathologic similarities between AMD and Alzheimer disease, including amyloidogenesis, plaque formation, inflammation, oxidative stress, and changes in glial cell function, 24 - 27 it is reasonable to hypothesize that similar calcium-dependent pathologic mechanisms occur in these 2 neurodegenerative diseases and are particularly harmful with increasing age.

We acknowledge that our study has several limitations. Assessment of calcium intake is based on an interview requiring participants to recall the supplements they ingested within the past 30 days and does not distinguish between those who took supplemental calcium for 30 days and those who may have been taking calcium supplements for many years.

In addition, self-reported calcium supplementation may not be accurately reflected by serum calcium levels. Previous studies 28 - 31 have found that oral calcium administration is associated with increases in plasma ionized calcium and urinary calcium and decreases in plasma parathyroid hormone.

However, there is a linear decrease in intestinal calcium absorption efficiency with increasing age, particularly after 40 years of age. Self-reported calcium supplementation may be inaccurate because of the ease with which consumption can be started and stopped. To summarize, limitations of our study include inaccuracy in reporting actual calcium supplementation and the lack of a strong correlation between such supplementation and serum calcium levels.

Finally, we found a potential association between self-reported supplemental calcium intake and AMD prevalence, but, as with any cross-sectional study, we cannot make any claims regarding causation, which would require longitudinal analysis to determine incident cases of AMD among those consuming varying amounts of calcium.

It is possible that the association we have found between self-reported calcium supplement consumption and AMD could be explained by some other underlying condition that is associated with both self-reported calcium consumption and AMD. It is also possible that the association is a chance finding.

Until further prospective studies are conducted to assess this association, we would not recommend that patients discontinue taking their calcium supplements in an attempt to reduce their risk of developing AMD, particularly given the known benefits of calcium supplementation for other medical conditions.

This result was most pronounced for individuals older than the year mean age of the AMD population, suggesting that there may be increased risk of developing AMD in individuals who ingest calcium for a longer duration or, alternatively, a greater propensity for calcium to cause harm in terms of AMD risk in the elderly population.

There was no dose-dependent response to increasing quintiles of self-reported calcium intake, which leads us to hypothesize that there is possibly a threshold above which the consumption of calcium may be a risk factor for the development for AMD and that this threshold may be below the recommended total daily intake of calcium in the United States.

Submitted for Publication: November 21, ; final revision received January 21, ; accepted February 1, Corresponding Author: Shan C. Lin, MD, Department of Ophthalmology, University of California, San Francisco, 10 Koret Way, Room K, San Francisco, CA LinS vision.

Published Online: April 9, Author Contributions: Dr Lin had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Acquisition, analysis, or interpretation of data: Kakigi, Wang, Enanoria, Lin. Critical revision of the manuscript for important intellectual content: All authors. Conflict of Interest Disclosures: None reported. The design and conduct of the study, analysis, interpretation of the data, and preparation of the manuscript were funded by the Clinical and Translational Research Fellowship Program.

Analysis was funded by core grant EY from the National Eye Institute, That Man May See Inc, and Research to Prevent Blindness.

Disclaimer: The contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health, University of California, San Francisco, or the Doris Duke Charitable Foundation.

full text icon Full Text. Download PDF Top of Article Abstract Introduction Methods Results Conclusions Article Information References. Table 1. Demographic and General Health Characteristics of Participants With and Without AMD a. View Large Download. Table 2. Health-Related Behaviors and Self-reported Supplement Use Among Participants With and Without AMD a.

Table 3. Odds Ratios for the Presence of Age-Adjusted Macular Degeneration Among Self-reported Supplementary Calcium Consumers vs Nonusers a.

Table 4. Odds Ratios for the Presence of Age-Related Macular Degeneration Among Self-reported Supplementary Calcium Consumers 68 Years or Older Compared With Nonusers a. Table 5. Odds Ratios for the Presence of Age-Related Macular Degeneration Among Self-reported Supplementary Calcium Consumers Aged 40 Through 67 Years vs Nonusers a.

Distribution of Demographics, Comorbidities, and Health-Related Behaviors by Quintiles of Self-reported Calcium Supplement Consumption eTable 2. Wong WL, Su X, Li X, et al. Global prevalence of age-related macular degeneration and disease burden projection for and Lancet Glob Health.

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The findings suggest that people who consume more than mg per day of supplementary calcium are 85 percent more likely to be diagnosed with AMD than those who do not supplement with calcium.

The association between supplementary calcium and AMD was found to be stronger in older individuals who often are the victims of AMD. This group of people was found to have taken calcium supplements over a longer period. Calcium is vital to maintain excellent health, but over-consumption can cause problems.

The findings about the link between calcium supplements and AMD should have an effect on how physicians—especially optometrists—speak to their patients about supplements.

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