Investigating the Effect of Coenzyme Q10 in the Treatment of Sudden Sensorineural Hearing Loss

EXTENDED ABSTRACT

Background

Sudden sensorineural hearing loss (SSNHL) is an acute otologic condition commonly defined as a decrease of approximately 30 dB across three consecutive frequencies occurring within three days or less [1]. It is usually unilateral; bilateral involvement is uncommon and has been reported in fewer than 5% of cases [2]. The degree and frequency pattern of hearing loss vary, and patients may also experience tinnitus, vertigo, or aural fullness [3]. Although infectious causes such as mumps, varicella-zoster virus, cytomegalovirus, and meningitis have been proposed [4, 5], vascular disorders, Meniere disease [6], and autoimmune mechanisms [7, 8] are also considered, while the cause remains unknown in many patients. Current therapeutic approaches include systemic or intratympanic corticosteroids, antiviral agents, hemodilution strategies, minerals and vitamins, batroxobin, hyperbaric oxygen, and other adjunctive measures [9-13]. Intratympanic steroid therapy has been reported to provide a recovery period comparable with systemic corticosteroid treatment [13].

Coenzyme Q10 is a potent antioxidant that can directly neutralize free radicals and participate in the recycling of other antioxidants [14, 15]. It has been studied for neuroprotective and mitochondrial effects in several disorders [16-18]. In relation to hearing disorders, patients with idiopathic SSNHL have been reported to have low serum coenzyme Q10 levels [19], and animal research has suggested that supplementation can reduce manifestations of age-related hearing loss [20]. On this basis, the present randomized clinical trial evaluated whether adding oral coenzyme Q10 to routine intratympanic dexamethasone therapy improves hearing recovery in patients with recent-onset SSNHL.

Methods

This randomized, placebo-controlled clinical trial was conducted in the Otorhinolaryngology Department of Besat Hospital, Hamadan. Sixty patients aged 18-70 years with SSNHL of less than one month duration were enrolled and allocated to intervention and control groups, with 30 patients in each group. Eligible participants had SSNHL and provided consent to participate. Exclusion criteria included a history of ear disease, calcium, vitamin, or magnesium supplementation during the specified period around the study, a cerebellopontine-angle mass or other ear pathology on magnetic resonance imaging, conductive hearing loss, and an interval of more than one month from SSNHL onset.

Before treatment, patients were evaluated for cerumen accumulation and acute or chronic middle-ear infection. Baseline audiologic assessment included tympanometry, pure-tone audiometry, speech reception threshold, and speech discrimination score, performed by the same audiologist. Magnetic resonance imaging was used to exclude tumoral lesions along the auditory nerve pathway. The groups were matched with respect to age, sex, affected ear, and the interval between symptom onset and presentation. Allocation was performed using 60 sealed opaque envelopes containing 30 intervention and 30 control assignments. Study medications were coded and visually identical, and the prescribing physician, patients, audiologist, and researcher were unaware of treatment content until data analysis was completed.

Both groups received routine treatment consisting of weekly intratympanic dexamethasone injections for three weeks. In addition, the intervention group received oral coenzyme Q10 at 100 mg/day for four weeks, whereas the control group received placebo tablets. Pure-tone hearing thresholds were assessed before treatment and again at the third and sixth months. Quantitative variables were summarized with measures of central tendency and dispersion. Normality was assessed with the Kolmogorov-Smirnov test. Statistical analyses included Student t test, Mann-Whitney test, repeated-measures analysis of variance, chi-square test, and paired Wilcoxon test, using SPSS version 26 with a significance threshold of P<0.05. The study was approved by the Ethics Committee of Hamadan University of Medical Sciences (IR.UMSHA.REC.1401.135) and registered in the Iranian Registry of Clinical Trials (IRCT20151123025202N23); written informed consent was obtained from all participants.

Results

The two groups were comparable at baseline. Each group included 16 men (53.3%) and 14 women (46.7%). The right ear was affected in 14 patients (46.7%) in the intervention group and 10 (33.3%) in the control group, while the left ear was affected in 16 (53.3%) and 20 (66.7%), respectively. No statistically significant between-group differences were found for sex (P=1.00), affected ear (P=0.29), age (P=0.06), or the interval between symptom onset and presentation (P=0.11).

Table 1. Baseline characteristics of patients by treatment group (N=60).

Before treatment, the mean pure-tone hearing threshold did not differ significantly between the groups (P=0.90). By the third month, the mean threshold was 29.33±15.96 dB in the intervention group and 35.34±12.24 dB in the control group, with a significant between-group difference (P=0.02). At six months, the corresponding values were 28.00±16.27 dB and 34.33±11.87 dB, respectively, and the difference remained significant (P=0.01). The overall difference in mean pure-tone hearing thresholds between intervention and control groups was also significant (P=0.00), supporting an effect of the coenzyme Q10 intervention. In addition, the combined effect of treatment timing and intervention on threshold improvement was significant (P=0.03), and the trajectory of recovery over six months was greater in the intervention group.

Table 2. Mean and standard deviation of pure-tone hearing thresholds by treatment group and assessment time (N=60).

Figure 1. Changes in mean pure-tone hearing thresholds by treatment group (N=60).

The distribution of hearing-loss patterns did not differ significantly between the groups before treatment or at the third and sixth months (Fisher exact test, P=0.51). In the intervention and control groups, respectively, the frequencies for similar loss across all frequencies were 4 (13.3%) and 6 (20.0%); high-frequency loss was observed in 2 (6.7%) and 4 (13.3%); and low-frequency loss occurred in 24 (80.0%) and 20 (66.7%). The perceived effect of hearing loss on quality of life was also not significantly different between the groups (P=0.63). Thus, the principal treatment signal was improvement in audiometric pure-tone thresholds rather than a demonstrable between-group difference in hearing-loss pattern or post-treatment quality-of-life impact.

Conclusion

In patients with SSNHL of less than one month duration, adding oral coenzyme Q10 at 100 mg/day for four weeks to routine intratympanic dexamethasone therapy produced greater improvement in pure-tone hearing thresholds than dexamethasone plus placebo, with significant differences evident at both three and six months. The findings support coenzyme Q10 as a potentially useful adjunct to standard intratympanic steroid treatment in this study population. The article also notes that follow-up was difficult for some patients and that quality of life was assessed only after treatment, limiting evaluation of change in that outcome.

Keywords: Coenzyme Q10, Sensorineural Hearing Loss, Treatment

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