Introduction

Tinnitus is the perception of sound in the absence of an auditory stimulus. Averaged over all age groups 5–15% of the western population experience some form of tinnitus. Many people can cope with chronic tinnitus, but about 1–2% of the population experience significant impairments in their quality of life due to their tinnitus.

The prevalence of chronic tinnitus increases with increasing age, peaking at 14.3% in people between 60 and 69 years of age [1]. The increase in tinnitus prevalence with age is at least partly explained by the fact that hearing loss is an important risk factor for tinnitus and hearing loss prevalence also increases with age [2].

Neuroplastic processes play a crucial role both in the generation of tinnitus [3] and in the amount of suffering [4]. Imaging studies reveal that neuroplastic changes in the central auditory system are generating the tinnitus percept [5] and that coactivation of nonauditory structures in the frontal cortex and the limbic system are involved in tinnitus related distress [6], .

Studies in animals and humans have shown that the mechanisms of cortical plasticity change over the lifetime with a tendency of decreased and less efficient neuroplastic potential as demonstrated by decreased induction and maintenance of long-term-potentiation (LTP) [8] and reduced long-term depression (LTD)-like effects with advancing age [9].

With these changes in the neuroplastic potential across the life span, age may not only have an influence on the incidence of tinnitus, but also on tinnitus related distress. A first hint for such a relation is given by a large epidemiological study demonstrating that people with bothersome tinnitus are elder than those with non-bothersome tinnitus (mean age 42 vs 38; p<0.001) [10]. Considering that tinnitus duration also influences its annoyance [11] we focused here especially on the role of tinnitus onset. In detail we hypothesized that the age of tinnitus onset may influence the perceived tinnitus related distress. More specifically, we assumed that early tinnitus onset is associated with less distress than later tinnitus onset.

Methods

Results

Prevalence of hearing impairment among tinnitus patients

Overall, 80.5% of participants (3,123 out of 3,878) complained about some form of hearing impairment. The prevalence of subjective hearing impairment increased with the age of the tinnitus patients. In the lowest quartile of the sample (16–48 years), 66.7% patients reported an impairment of their hearing, which increased to 85.9% in the oldest quartile (64–95 years, see figure 1a).

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Figure 1. Graphical illustration of the sample data and results.

a) The prevalence of hearing impairment increases with the participant's age. Prevalence data were aggregated with respect to age quantiles (Q1: 16–48 years, Q2: 48–57 years, Q3: 57–64 years, Q4: 64–95 years). Figures b) and c) report data from the group of subjects without subjectively reported hearing impairment. b) Histogram of the participant's age at tinnitus onset. c) Tinnitus distress increases with the age of tinnitus onset. The data were aggregated with respect to the age of onset quartiles (Q1: <32 years, Q2: 32–42 years, Q3: 42–53 years, Q4: 53–72 years). d) The percentage of patients that describe their tinnitus as “distressing from the beginning” increase for older age of onset. For illustration purposes, the sample was stratified as quartiles from early (1st quartile: tinnitus onset before the age of 32) to later tinnitus onset (2nd quartile: age 32–42; 3rd quartile: age 42–53; 4th quartile: over age 53). We found that the percentage of patients describing their tinnitus as distressing from the beginning augments with the tinnitus onset age 69.9 in the first quartile) up to 83.3% in the oldest quartile.

https://doi.org/10.1371/journal.pone.0027379.g001

Discussion

The main finding of our analysis is an influence of the age at tinnitus onset on tinnitus related distress. Higher age at tinnitus onset is associated with higher tinnitus related distress. To our knowledge this is the first report about an influence of age of tinnitus onset on tinnitus severity. This effect is independent from the age at tinnitus assessment, the duration of tinnitus and the type of tinnitus onset (gradual versus abrupt).

A large variety of different variables have been identified in the past as contributing factors to tinnitus distress, among them tinnitus loudness, hearing loss, vertigo/dizziness, hyperacusis, depression, anxiety and personality factors [11], [12], [16], [17]. Our study adds “age of onset” as an additional influencing factor underscoring the relevance of time related aspects in the pathophysiology of tinnitus. Earlier studies identified age and tinnitus duration as relevant factors. Age is strongly influencing tinnitus prevalence [1] and tinnitus duration plays an important role for response to treatment [18]–[21]. Though the effect of age of onset is statistically highly significant, it is rather small. However, considering the many variables, which exert a known influence on tinnitus related distress, this is not surprising.

Even though we cannot derive direct implications of our results on the clinical management of tinnitus patients, they may be relevant for a better understanding of both physiologic changes of brain function with increasing age and the pathophysiologic mechanisms involved in the generation of tinnitus distress. Many aspects of brain structure, brain function and brain plasticity are changing with age in a complex way [22]. These changes also involve adaptive and compensatory neural mechanisms [23]. Both the generation of tinnitus and the amount of tinnitus distress are thought to depend on adaptive and compensatory brain mechanisms [4]. In this context higher tinnitus distress at higher age of onset suggests an age-related decline in the efficiency of this compensatory mechanism for tinnitus. Thus our finding is in line with the observation that a decrease of cognition is related to higher tinnitus related distress [24]. Future studies are invited to further characterize the interactions between age related changes in neuroplastic potential, cognitive function and their influence on tinnitus distress.

Some limitations on the data analysis need to be noted here: The presented analysis is based on data from self report questionnaires of individuals with tinnitus and subjectively normal hearing. This selected sample may not be representative for all patients with tinnitus [25]. Also, the sample is restricted to active members of the German tinnitus patient association, which implies first a local selection and second a selection to people who are impaired by their tinnitus. Therefore, we are aware that our conclusions can only be preliminary as long as these data are not replicated in further independent samples. However, earlier analyses based on the same sample have provided results [8], [9], which are in line with the literature, indicating that the dataset is representative.

Tinnitus related distress is influenced by many variables such as tinnitus loudness, hearing loss, vertigo/dizziness, hyperacusis, depression, anxiety and personality factors. Here we suggest that the age at tinnitus onset might be an additional factor. Patients with a later onset of tinnitus in their life report greater distress than patients with an early tinnitus onset. The decline of neuroplasticity with advancing age might be an underlying mechanism for this observation.

Acknowledgments

We want to thank the German Tinnitus League for giving us the opportunity to analyse their dataset.