Tinnitus, hearing loss, cognition and infection in adults and children

In an era of increased longevity, society is facing new health care issues such as hearing loss, tinnitus, cognitive impairment and dementia. The risk factors  of hearing loss and tinnitus and its associations with cognition are till date unclear. Therefore in this study we will focus on four research questions, which we will shortly introduce per question below. 

1.cognition and hearing 
Dementia is a disorder that is characterized by cognitive decline involving one or more domains (learning and memory, language, executive function, complex attention, perceptual-motor, social cognition) interfering with daily function and independence.1 Mild cognitive impairment (MCI) is an intermediate clinical state between normal cognition and dementia whereby a greater extent of cognitive decline is demonstrated than would be expected by normal aging.1,2 While specific subtle changes in cognition can occur in normal aging, MCI can be a precursor to dementia.2 

Considering the wide range of degrees of cognitive impairment with implications to people’s life, it is considered one of the greatest global challenges for health and social care in the 21st century. 3The WHO published that in 2015 the total global societal cost of dementia was estimated to be US$ 818 billion, equivalent to 1.1% of global gross domestic product (GDP) which underlines the social and economic implications of this condition.4 Acting upon preventing cognitive decline during life will vastly improve the lives of millions of individuals. 

In 2017 the Lancet stated that 35% of the risk factors for dementia are adjustable, and that hearing loss is recognized as a potential cause entailing  9% of the risk of dementia over a life course. Non-congenital sensorineural hearing loss (SNHL) usually comes with aging, and usually starts with subtle symptoms; having to turn the television louder, or missing words in a conversation. Many patients only seek help after the hearing loss gets severe.5 In the US about 15%,6 and in the Netherlands it is estimated that one third of affected patients use hearing aids. 

The alarming effect of the lack of treatment of hearing loss is not only worrying for the hearing and social abilities of those patients, as stated earlier, hearing loss is recognized as causing 9% of the risk of dementia. The exact underlying mechanism of this relationship is unclear, but two potential hypothesis are proposed. First, SNHL and cognitive loss might have common neurodegenerative causes, secondly, downstream neural changes precipitated the diminished auditory input. Core of these hypotheses is the theory that the diminished auditory input profoundly affects speech processing capabilities and consequently impair social functioning.7 

While hearing amplification with hearing aids is a low-cost intervention compared to the high costs for the psychosocial and cognitive problems which can result from hearing loss, till date, the evidence base for the effect of hearing amplification as preventive measure for cognitive decline is weak. 8 In this proposal we aim to study the relationship between self-reported hearing limitation, use of hearing aids and cognitive function over time. 

16-21% of the adult population are bothered by tinnitus at some point in their life and 10-15% of the general population experience tinnitus severely enough to seek medical attention.9 2-3% of the adult population is severely impaired by tinnitus, which means they can-not participate in normal daily activities.10 

2 and 3. Tinnitus in adults and children 
Tinnitus is the perception of sound without an external stimulus11, often experienced as a ringing or buzzing sound.12,13 The exact prevalence is difficult to determine, it is believed that around 21% of the population experience tinnitus regularly and that about 10-15% of the general population experience tinnitus severely enough to seek medical attention.9 most studies to date have been conducted in high risk populations and definitions of tinnitus vary.14

Tinnitus is a heterogeneous condition. This heterogeneity manifests in differences in the perceptions of tinnitus itself, e.g. sound, frequency and loudness, and in differences in accompanying symptoms like depression, anxiety, sleep and somatic problems. Therefore, the burden and impact on individuals with tinnitus varies substantively, from chronic and disabling to no burden at all. 15,16 

Evidence regarding the associations between tinnitus and various aspects of health is mainly studied in high risk populations 17–19 and few included both demographics, general and mental health issues In a recent cross-sectional study of our research group we investigated general and mental health factors in relation to tinnitus presence and burden in an Australian population study (Stegeman et al, 2020, submitted).

The disadvantage of those cross sectional studies is that it remains unclear if health problems like cardiovascular disease, depression or pain cause tinnitus, or if the causation is the other way around.

Therefore in this study we want to assess the longitudinal relation between mental, general health and tinnitus. 

Tinnitus in Children 
Insights in tinnitus prevalence and related distress are mainly based on research in adulthood. Moreover, according to the WHO, 1.1 billion young people (aged between 12-35 years) are at risk of noise- induced hearing loss and numbers of children with disabling hearing loss are  rising.8 Hearing loss is often accompanied by tinnitus which is thereby  an increasing problem in children and young adults.

So far, literature is scarce about  the incidence, the burden and contributing factors in the presence of tinnitus and n  in children. Considering the devastating effects of tinnitus in adults, such as sleeping difficulties, concentration problems and a reduction in quality of live, the presence and effects of tinnitus on behavior in children is worthwhile studying. Therefore, as a first step in tinnitus research we aim to assess the prevalence of tinnitus in a young population of non-institutionalized children and adolescents with and without hearing loss. 

4. Infection and children 
There are significant gaps in our knowledge of the influence of infections in hearing outcomes in later life. In children, several peri‐ and post‐natal risk factors have been demonstrated to be related to early childhood hearing loss (JCIH 2019 position paper).

However, whether the occurrence of ear infections or other upper respiratory tract infections in childhood is associated with hearing loss in young adults is unknown. The few studies so far addressing this question were hindered by short follow-up, retrospective design of the study or focused at a selective type of upper respiratory tract infection. 2021A longitudinal study detailing the occurrence and type of childhood infection could answer the question as to whether these variables are related to the onset of hearing loss in young adults.