Hearing impairment, cardiovascular disease risk factors, methylmalonic acid, and vitamin B12 status in older adults
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Hearing impairment is a common chronic health condition in older adults and is associated with impaired quality of life. However, there is limited comprehensive research concerning interactions among poor diets and hearing loss. In the first study, the prevalence of hearing impairment and the relationship of Hearing Handicap Inventory for the Elderly with pure-tone average threshold (PTA) were evaluated. Approximately 63% of participants had hearing impairment in the best ear [PTA across 1, 2, and 4 kHz > 25 dB hearing level (HL)]. A moderate correlation was found between Hearing Handicap Inventory for the Elderly and PTA. In the second study, the relationship between hearing loss and cardiovascular disease (CVD) risk factors was examined. Low-density lipoprotein cholesterol, total cholesterol, and triglycerides were not significantly associated with hearing loss. However, PTA was significantly correlated with high-density lipoprotein (HDL) cholesterol in the poorest ear and total cholesterol/HDL cholesterol ratio in both ears. Participants with impaired hearing had significantly lower HDL cholesterol concentration than those with normal hearing (d 25 dB HL) in the worst ear. Participants with PTA > 40 dB HL had significantly lower HDL cholesterol level than those with PTA d 40 dB HL in both ears. Thus, HDL cholesterol may be a modifiable risk factor for hearing loss. In the third study, the relationship between age-related hearing loss (ARHL) and poor vitamin B status in older adults was examined, using multiple measures of vitamin B 12 status and by repletion with a vitamin B12 supplement. A consistent relationship of vitamin B12 with auditory function was found in the worst ear. Participants with impaired hearing in the worst ear had a significantly higher prevalence of vitamin Bdeficiency, higher mean serum MMA concentration, higher prevalence of elevated MMA (> 271 nmol/L), and a non-significantly higher prevalence of low serum vitamin B12 than those with normal hearing (d 25 dB HL). Hearing thresholds were not improved in any group after three months of vitamin B 12 supplementation (0-1000 µg/d). Impaired vitamin B12 status may be a modifiable risk factor for ARHL in older adults. Since vitamin B12 repletion did not improve hearing function in vitamin B deficient participants, this suggests that prevention of vitamin B deficiency may be important. This research adds to the growing body of literature that suggests CVD- and nutrition-related risk factors are associated with hearing loss in older people.