Effects of folic acid supplementation on hearing in older adults: a randomized, controlled trial.
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.


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


METHODS
The Netherlands.


METHODS
728 older men and women recruited from municipal and blood bank registries with plasma total homocysteine concentrations 13 micromol/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.


METHODS
Daily oral folic acid (800 microg) or placebo supplementation for 3 years.


METHODS
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.


CONCLUSIONS
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.
Durga
Jane
J
Wageningen University and Wageningen Centre for Food Sciences, Wageningen, The Netherlands. jane.durga@rdls.nestle.com
Verhoef
Petra
P
Anteunis
Lucien J C
LJ
Schouten
Evert
E
Kok
Frans J
FJ
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001309:Auditory Threshold; D019587:Dietary Supplements; D004311:Double-Blind Method; D005260:Female; D005492:Folic Acid / Q000008:administration & dosage* / Q000097:blood; D006319:Hearing Loss, Sensorineural / Q000097:blood / Q000503:physiopathology / Q000517:prevention & control*; D006710:Homocysteine / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged
D006710:Homocysteine; D005492:Folic Acid