Effects of Folic Acid Supplementation on Hearing in Older Adults

A Randomized, Controlled Trial

2 January 2007 | Volume 146 Issue 1 | Pages 1-9

Background: Age-related hearing loss is a common chronic condition of elderly persons. Low folate status has been associated with poor hearing.

Objective: To determine whether folic acid supplementation slows age-related hearing loss.

Design: Double-blind, randomized, placebo-controlled trial conducted from September 2000 to December 2004.

Setting: The Netherlands.

Participants: 728 older men and women recruited from municipal and blood bank registries with plasma total homocysteine concentrations 13 µmol/L or greater serum and vitamin B₁₂ concentrations 200 pmol/L or greater at screening, and no middle ear dysfunction, unilateral hearing loss, or pathologic ear conditions unrelated to aging.

Intervention: Daily oral folic acid (800 µg) or placebo supplementation for 3 years.

Measurements: 3-year change in hearing thresholds, assessed as the average of the pure-tone air conduction thresholds of both ears of the low (0.5-kHz, 1-kHz, and 2-kHz) and high (4-kHz, 6-kHz, and 8-kHz) frequencies.

Results: Initial median hearing thresholds were 11.7 dB (interquartile range, 7.5 to 17.5 dB) for low frequencies and 34.2 dB (interquartile range, 22.5 to 50.0 dB) for high frequencies. Sixteen participants (2%) were lost to follow-up. After 3 years, thresholds of the low frequencies increased by 1.0 dB (95% CI, 0.6 to 1.4 dB) in the folic acid group and by 1.7 dB (CI, 1.3 to 2.1 dB) in the placebo group (difference, –0.7 dB [CI, –1.2 to –0.1 dB]; P = 0.020). Folic acid supplementation did not affect the decline in hearing high frequencies.

Limitations: The strict criterion for participation on the basis of serum homocysteine concentrations limits extrapolation to the general population. Folic acid fortification of food was prohibited in the Netherlands during the study, so baseline folate levels in participants were about half of those found in the U.S. population.

Conclusions: Folic acid supplementation slowed the decline in hearing of the speech frequencies associated with aging in a population from a country without folic acid fortification of food. The effect requires confirmation, especially in populations from countries with folic acid fortification programs.

Clinicaltrials.gov identifier: NCT00110604.

Editors' Notes Context Epidemiologic evidence suggests an association between folate and homocysteine levels and hearing status. Contributions The investigators randomly assigned 728 older adults with high homocysteine levels to receive daily folic acid or placebo for 3 years. They found that hearing thresholds for low frequencies increased more slowly in participants taking folic acid, suggesting a protective effect. Cautions The trial was conducted in the Netherlands at a time when folate fortification of food was prohibited. Implications Folic acid supplementation seemed to slow the decline of low-frequency hearing in folate-deficient, older adults. —The Editors

 

Author and Article Information

From Wageningen University and Wageningen Centre for Food Sciences, Wageningen, the Netherlands, and University Hospital Maastricht, Maastricht, the Netherlands.

Acknowledgments: The authors thank all study participants for their time and motivation; the Folic Acid and Carotid Intima-media Thickness (FACIT) trial research team for their dedication and enthusiasm; Mickey Chenault, University Hospital Maastricht and Heinsius Houbolt Foundation, for data verification; and Martijn Katan, Wageningen University and Wageningen Centre for Food Sciences, for critical comments on the manuscript.

Grant Support: By the Netherlands Organisation for Health Research and Development (ZonMw, grant no. 20010002), Wageningen University, and Wageningen Centre for Food Sciences.

Potential Financial Conflicts of Interest: None disclosed.

Requests for Single Reprints: Jane Durga, PhD, Cognitive Sciences Group, Nutrition & Health Department, Nestlé Research Center, PO Box 44, CH-1000 Lausanne 26, Switzerland; e-mail, jane.durga{at}rdls.nestle.com.

Current Author Addresses: Dr. Durga: Cognitive Sciences Group, Nutrition & Health Department, Nestlé Research Center, PO Box 44, CH-1000 Lausanne 26, Switzerland.

Dr. Verhoef: Nutrition Department, Unilever–UFHRI, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands.

Dr. Anteunis: Department of Otorhinolaryngology, Division of Audiology, Brain, and Behavior Institute, University Hospital Maastricht, 6200 MD Maastricht, The Netherlands.

Dr. Schouten: Food and Consumer Product Safety Authority, PO Box 19506, 2500 CM The Hague, The Netherlands.

Dr. Kok: Division of Human Nutrition, Wageningen University, PO Box 8129, 6700 EV Wageningen, The Netherlands.

Author Contributions: Conception and design: J. Durga, L.J.C. Anteunis, E. Schouten.

Analysis and interpretation of the data: J. Durga, L.J.C. Anteunis, E. Schouten.

Drafting of the article: J. Durga, L.J.C. Anteunis, E. Schouten.

Critical revision of the article for important intellectual content: J. Durga, P. Verhoef, L.J.C. Anteunis, F.J. Kok.

Final approval of the article: J. Durga, P. Verhoef, L.J.C. Anteunis, E. Schouten, F.J. Kok.

Provision of study materials or patients: J. Durga.

Statistical expertise: J. Durga.

Obtaining of funding: J. Durga, P. Verhoef, E. Schouten, F.J. Kok.

Administrative, technical, or logistic support: J. Durga, P. Verhoef.

Collection and assembly of data: J. Durga, E. Schouten.