The European Tinnitus Survey: a Cross-sectional Observational Study on Tinnitus Prevalence in 12 European Countries
Conditions: Tinnitus
Sponsor: Mario Negri Institute for Pharmacological Research

The European Tinnitus Survey: a cross-sectional observational study on tinnitus 
prevalence in 12 European countries 
 
 
Date: 4 May 2021 
NCT ID not yet assigned 
 
 

 
BACKGROUND AND RATIONALE 
Tinnitus is a common symptom of clinically heterogeneous pathologies and is defined as the 
conscious perception of an auditory sensation in the absence of a corresponding external 
stimulus.1 Tinnitus, in its debilitating form, negatively affects emotional health and social well-
being2, and can precipitate psychological distress severe enough to cause self-harm and 
suicidal ideations3,4, while exerting substantial individual and societal financial burden.5,6 
Therefore, it becomes crucial to take adequate preventive measures and health interventions. 
According to population-based studies from Western Europe and US, tinnitus prevalence lies 
between 10% and 15%.1 Nonetheless, there is a lack of clear understanding of global 
prevalence of tinnitus. Inherent methodological drawbacks and between study differences 
hinder deriving a global estimate by pooling data from studies conducted in different countries 
and world regions.1,7,8 Therefore, uncertainties with regards to the prevalence of tinnitus remain.  
Being a subjective condition, the impact of tinnitus symptoms depends on its perceived 
bothersomeness or severity. Therefore, “bothersome” or "severe" tinnitus symptoms are a better 
predictor for the emotional, societal and financial burden of tinnitus than "any" tinnitus.5,6 The 
economic burden is directly related to the severity of the tinnitus symptoms, with increased 
healthcare costs in people with severe tinnitus. In a study conducted in the Netherlands, the 
mean annual costs per patient was €767 for mild, €1329 for moderate and €2218 for severe 
tinnitus.5 A similar pattern was noted in a study in USA, where medical costs were reported to 
be directly proportional to severity of tinnitus.9 While epidemiological studies have attempted to 
distinguish any and severe tinnitus, both these concepts are troubled by heterogeneous 
prevalence estimates.8 Hearing difficulty is a major risk factor for tinnitus and often co-occur in 
an individual.1 However, not many studies have measured the prevalence of tinnitus in a 
population with hearing difficulty.  
 
OBJECTIVE 
The primary objective of this population-based cross-sectional study is to estimate the overall 
and country specific prevalence of any tinnitus, bothersome tinnitus, and severe tinnitus in 12 
European Union (EU) countries. 
The study data have been analyzed to fulfil the following secondary objectives: 
• 
To examine inter-country differences in prevalence of tinnitus by making the following 
comparisons: 
o Comparing prevalence estimates in countries with relatively low versus high gross 
domestic product (GDP) per capita 
o Comparing prevalence estimates in countries within different European regions (i.e., 
Northern, Southern, Eastern and Western Europe) 
• 
To understand the effect of sex, age, socio-economic variables, body mass index (BMI), and 
marital status on overall prevalence of tinnitus 
• 
To assess the effect of hearing difficulty on tinnitus prevalence 
• 
To explore the effect of tinnitus severity on use of healthcare resource for tinnitus 
 

METHODS 
Study design 
To achieve the aims of this study, we conducted face-to-face population-based cross-sectional 
survey in 12 strategically selected EU28 countries (Bulgaria, England, France, Germany, 
Greece, Ireland, Italy, Latvia, Poland, Portugal, Romania, and Spain). The study methodology is 
similar to another Pan-European survey on second-hand smoking and e-cigarettes, the 
TackSHS Project (“Tackling secondhand tobacco smoke and e-cigarette emissions: exposure 
assessment, novel interventions, impact on lung diseases and economic burden in diverse 
European populations”; www.tackshs.eu) conducted in the same 12 countries in 2017-2018, 
funded by the European Commission (EC) within the Horizon 2020 research grants (grant 
agreement number: 681040).10  
For each country, the study sample is representative of the general population aged 18 years 
and above in terms of age, sex, geographic area, and socio-economic characteristics. Multi-
stage methodology was used as the preferred sampling methodology. In the first stage, the 
primary unit of selection was geographic area or voting center. In the second stage, households 
or municipalities were selected. In the last stage, respondents were chosen randomly, in order 
to be representative of the population. Other methods, including stratified or simple sampling or 
quota methods, were also accepted wherever it is not possible to conduct a multistage random 
sampling.  
Selection of countries 
For the present study, an appropriate sample of 12 European countries–all EU28 Member 
States (MS) –representing geographical, legislative and cultural variations across the EU, have 
been selected. The selected European countries are as follows: Bulgaria (BG), England (UK), 
France(FR), Germany(DE), Greece (GR), Ireland (IE), Italy (IT), Latvia (LV), Poland (PL), 
Portugal (PT), Romania (RO), and Spain (ES). These countries were selected after taking into 
account several aspects, including: i) different geographical distribution; ii) different level of per 
capita income. According to geographic area, we considered countries from northern (IE, UK), 
central/western (DE, FR), central/eastern (BG, LV, PL, RO), and southern Europe (ES, IT, GR, 
PT). Moreover, the selection includes the 7 most populated EU28 MS (DE, ES, FR, IT, UK, PL, 
RO), and, among less populated countries, we prioritized middle-income countries (BG, RO). 
Overall, the 12 selected EU MS represent 78.8% of the EU28 overall population. 
Study population 
In each of the 12 selected European countries, approximately 1000 individuals, representative 
of the general population aged 18 years and above in terms of age, sex, geographic area, and 
socio-economic characteristics, were enrolled in this cross-sectional study. The final sample 
therefore includes a total of 11,427 subjects. 
Inclusion criteria 
• 
individuals aged 18 years and above 
• 
individuals who are residents of the 12 selected countries 
• 
individuals able to understand and answer the questions of the study questionnaire in 
the country-specific language 
• 
individuals who formally accept to participate in the study 

Exclusion criteria 
No specific exclusion criteria are considered 
Sample size computation 
The sample size for each country allowed us to obtain prevalence estimates with a maximum 
standard error (SE) lower than ± 1.6%. Therefore, with such a sample size we have been able 
to provide stable prevalence estimates (with a relatively small 95% confidence interval), both 
overall and country-specific.  
Data collection 
In each country, individuals were surveyed by trained interviewers through face-to-face 
interviews using a structured standardized questionnaire. Data collection was coordinated by 
DOXA, a leading market research organization and Italian branch of the Worldwide Independent 
Network/Gallup International Association (WIN/GIA), and performed in collaboration with its 
European partners (see “Selection of the subcontract or performing data collection” paragraph). 
Data was collected within computer assisted personal interviews (CAPI). The fieldworks lasted 
two to three months in each country. The English version of the questionnaire has been 
developed by collaborators from University of Nottingham (UK) University of Regensburg 
(Germany), and Mario Negri Institute (Italy). Before fieldwork, the tinnitus-related questions were 
translated from English into various country-specific languages using the good practice 
guidelines for questionnaire translation. The details of the translation process have been 
published as a technical note.11 
The country-specific information provided by DOXA and its European partners for each 
European country include information on sampling methodology (e.g., sampling method used, 
response rate, fieldwork dates, age range). The survey questionnaire is designed to collect 
individual-level information for each survey participant, and is divided in two sections. The first 
section provided information on: socio-economic and demographic characteristics (e.g., sex, 
age, level of education, and profession). The second section provided information on tinnitus 
prevalence, tinnitus severity, healthcare resource use for tinnitus, and hearing difficulty 
prevalence. 
Statistical analysis plan 
Creation of the survey dataset 
Once the fieldwork was completed, DOXA collected data from its European partners and after 
internal checks provided to Mario Negri Institute the 12 anonymous data files in text format, with 
the corresponding codebook in English language. The 12 data files were managed by the team 
at the Laboratory of Lifestyle Epidemiology, Department of Environmental Health Sciences of 
Mario Negri Institute. Using the statistical package SAS, version 9.4 (SAS Institute, Cary, NC, 
USA), they performed the input of the 12 textual data file into 12 corresponding SAS datasets, 
and then created a unique final dataset in SAS. This dataset was checked for coherence and for 
the presence of possible errors, cleaned, and finalized through the generation of queries which 
were addressed by DOXA and its European partners.  
Statistical analyses 

Statistical analyses required to achieve objectives has been conducted by the teams from the 
Laboratory of Lifestyle Epidemiology, Department of Environmental Health Sciences of Mario 
Negri Institute and the University of Nottingham, using SAS statistical package. Prevalence of 
three working definitions of tinnitus (any, bothersome and severe tinnitus) have been estimated 
through univariate statistical analyses (i.e., descriptive statistics for categorical data, including 
absolute or relative frequencies), overall, by country, and in strata of selected demographic and 
socio-economic (individual and country-specific) characteristics. Continuous variables have 
been summarized through the use of means and standard deviations. Alternatively, they have 
been categorized, and thus described through absolute or relative frequencies.  
Multivariate analyses have been conducted to identify sub-groups of the population (e.g., based 
age-groups, low vs. high educated subjects) or clusters of countries (e.g., based on income 
levels and regional groups) where tinnitus is more frequent. Thus, odds ratios (OR), and the 
corresponding 95% confidence intervals (CI), were estimated through logistic regression models 
after adjustment for selected individual-level characteristics. 
 
ETHICAL AND ADMINISTRATIVE ASPECTS 
Informed consent 
At recruitment, information on survey characteristics was given to all participants by suitably 
qualified professionals, who were able to provide answers to any possible questions and to 
eliminate any concern respondents may have. Information explaining the condition (i.e., tinnitus) 
was provided to survey participants in the country-specific language in a clear, jargon free 
manner, using fully understandable terms and language.  
Although in EU countries, according to their current legislation, written consent is not mandatory 
for this type of study (observational study collecting anonymized information), all participants 
were asked to sign the informed consent form for participation in the study. Since data was 
collected with CAPI method (using computer or tablet), participants had the possibility to tick an 
electronic document in order to express their willingness to participate in the study. No written 
signature was required.  
Privacy observance procedures 
Survey data was stored in electronic format. Only a selected number of pre-designated 
members of the data collection team had access to the password protected laptops. Once data 
collection was complete, all data had been uploaded into a single database and reliably and 
completely deleted from the laptops. Selected personal data, including the names of 
respondents, was collected to enable quality assurance procedures and to allow participants 
willing to withdraw from participation in the survey to have their records deleted from the 
database. Once quality assurance procedures were complete (within 4 months of the 
completion of data collection), names and other unique personal identifiers (such as full 
address) were reliably and completely deleted. During the quality assurance procedures, Mario 
Negri Institute obtained an anonymous copy of the analysis database, i.e., without names of 
participants but with encrypted (not personally identifiable) codes. The encryption key is kept by 
DOXA and its European partners in a place separated from the research group. All access to 
the encryption key was logged. This encryption key was destroyed once quality assurance 

procedures are complete. After this procedure, there was no possibility to identify the participant 
record and consequently to delete it from the database. The analysis database is held securely 
on a password protected file server at Mario Negri Institute, and only a limited number of 
researchers from the research team have access to this analysis database. All data is managed 
anonymously, in respect of the privacy regulations in force, only for scientific purposes, without 
any lucrative aim. Moreover, results of the study do not consist any individual-level data, but 
aggregated data, and summary results are disseminated, thus not allowing to identify the survey 
participants. These and other measures are in agreement with national and current or 
forthcoming EU (i.e., Directive 95/46/EC) regulations. The Ethics Committee of the study 
coordinator (Ethics Committee of Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, 
Italy) notified that no preventative evaluation was required for the present study, since 
anonymous data was collected (File number 37/2017).  
Access to personal data and withdrawal from the study 
In this survey no sensitive personal data (e.g., health, sexual lifestyle, ethnicity, political opinion, 
religious or philosophical conviction), genetic information, or data involving tracking or 
observation of participants was collected. According to other personal data, it was made clear 
that subjects are completely free to withdraw their records from participation in the survey, and 
that the consent given by participants in the study can be withdrawn, without any explanation or 
justification. In this case, all data pertaining to the subjects in question was destroyed. 
Selection of the subcontractor performing data collection 
The development of the questionnaire and the data managing, analysis and interpretation have 
been carried out by the Laboratory of Lifestyle Epidemiology, Department of Environmental 
Health Sciences of Mario Negri Institute, in collaboration with partners from University of 
Nottingham and University of Regensburg. For cost-effectiveness and efficient fieldwork, data 
collection of the European cross-sectional survey was delegated to a leading market research 
organization, DOXA, which was involved as a subcontractor of Mario Negri Institute. Mario Negri 
Institute has collaborated with DOXA in several national and international projects, including the 
annual national surveys on smoking since 2001 (in Italy), and in the PPACTE and the TackSHS 
project, involving 18 and 12 European countries, respectively. Therefore, the collaboration has 
been established before the beginning of the study. 
Ownership of the data 
Individual-level anonymous data sent from DOXA and its European partners, and stored at the 
Mario Negri Institute, are the property of the study coordinator.  
 
RELEVANCE AND IMPLICATIONS 
One of the expected outcomes of this study is the first estimate of tinnitus prevalence from a 
Pan-European study. Given the lack of standardized tinnitus prevalence questions and a global 
prevalence estimate, this study provides both standard assessment measures and an estimate 
of how prevalent tinnitus symptoms are. McFerran and colleagues identified the lack of an 
agreed prevalence estimate as one of the most crucial hindrances to engaging the 
pharmaceutical industry in searching for a tinnitus cure.12 In this study, we report the prevalence 
of any tinnitus using the same set of research questions in various languages. This measure 

identifies the commonality of the condition. Furthermore, we assess the proportion of individuals 
having bothersome and severe symptoms, who exert the true burden on financial and personnel 
resources in the healthcare system. These estimates measured in a Pan-European study 
demonstrate the size of the problem. This can guide resource allocation for implementing 
effective measures and attract various stakeholders, including research funders, industrial and 
healthcare organizations, to engage in needful endeavors for tackling tinnitus. 
 
DISSEMINATION 
The main channels of dissemination of the results of this survey will be international peer-
reviewed open-access journals. Open access journals will allow the free dissemination of the 
study’s results among the scientific community. The dissemination will be followed critically and 
professionally, to maximize the study’s impact on both scientific knowledge and on public 
health. Key findings from this study have been presented in hearing and tinnitus related 
conferences, and other varied forms of communications have been used to promote awareness 
of the study results to organizations and stakeholders involved in the hearing and tinnitus 
research, health promotion, and public health. 
 
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