How widespread is age-related vestibular loss?

The inner ear balance system, also called the vestibular system, deteriorates with age just like the rest of the body. This may sound logical, but we are presently only starting to fathom the extent of the consequences of this process. Yuri Agrawal MD addressed this issue during the Academic Research Conference on March 25, 2015, linked to Audiology NOW! 2015 in San Antonio. “The problem doesn't only regard a small specific population, as was thought until recently, but perhaps a high percentage of all elderly to some degree. This is highly relevant, as vestibular loss has profound direct effects - for instance fall incidents. It has also indirect effects such as loss of confidence and anxiety disorders, resulting in decreased mobility and disability. We are increasingly recognizing vestibular loss as an important health issue.”

“Traditionally, loss of vestibular function is regarded from the perspective of specific diseases, that only affect a small part of the population”, says Yuri Agrawal MD, Assistant Professor in the Department of Otolaryngology at Johns Hopkins University School of Medicine. Examples of these specific diseases are Meniere’s, benign paroxysmal positional vertigo (BPPV) and vestibular neuritis. Agrawal: “But there is increasing evidence that vestibular loss may affect a larger segment of this population, specifically the elderly, caused by a more general deterioration of the peripheral and central vestibular systems.” This structural deterioration may cause vestibular reflex deficits and dizziness.

“Explanations for the gradual decline can be found in hair cell death and decline of the afferent nerves that innervate the hair cells”, says Agrawal. Everybody knows and expects that vision and hearing tend to decline when the number of years rises, and it now appears that the same happens with the vestibular system. “Instead of related exclusively to quite rare and specific afflictions, it looks very much like it that in reality it involves a much more widespread health problem”, Agrawal concludes.

Grave consequences

Apart from the prevalence of the problem, the gravity of its consequences makes it also something to take very seriously. Agrawal: “Vestibular loss leads to increased risk of falling. Because of this people lose confidence and their mobility is restricted.” Statistics show how grave these consequences are. Between twenty and forty percent of people over 65 years of age who live at home fall each year. Research by Hoffman and Sklare in 2006 has shown that older people with chronic dizziness or imbalance are two to three times more likely to fall in comparison with peers who don't experience these problems. Furthermore, a considerable percentage of the elderly who end up with a hip fracture because of such a fall, die within a year.

There is more scientific evidence to underline the seriousness of the consequences of vestibular loss, Agrawal indicates: “'Gait speed', or walking velocity in elderly people is a very important geriatric assessment tool. It provides a powerful prediction for both morbidity and mortality. There appears to be a link between vestibular dysfunction and reduced gait speed. Also, there is pretty robust evidence in literature about the relation between vestibular dysfunction and anxiety disorders.”

How much of these alarming facts should be contributed to vestibular loss? Agrawal: “It is difficult to isolate the influence of vestibular loss in the complex of origins behind lessened gait speed – and fall incidents, for that matter. Large population-based analyses can be helpful here: when you assess enough people, you can measure various factors and focus on the cases in which all other factors except gait speed and vestibular loss remain constant. And especially when you combine these large datasets with laboratory experiments including normal healthy people, you can get an estimate for the contribution of vestibular loss on this health problem.”

High prevalence

There is already some knowledge available, but there is more work to be done. As insight on the prevalence of the problem has just recently begun to be gained, the present statistical evidence is still rather limited. Agrawal: “In a German study conducted by neurology professor Hannelore Neuhauser of the Charité University of Berlin, based on a telephone interview survey with several thousands of adult participants, an overall prevalence of vestibular vertigo of seven to nine percent was found. This prevalence increased with age to fifteen percent in the oldest category of people over eighty-five. This is one estimate of the prevalence based on validated questionnaire data.”


Agrawal conducted her own research for vestibular function within the scope of the National Health and Nutrition Examination Survey (NHANES) using an objective though less specific test of vestibular function. “The figures we found were much higher as the data on vertigo in the German study. We saw as much as thirty-five percent suffering from vestibular loss in adults and even eighty-five percent of the population over eighty years of age.” Apart from that, in Baltimore there is a broad Longitudinal Study of Aging going on, in which Agrawal's research group also gathers data on the vestibular system.

Towards standardization

The large variation in prevalence estimates justifies several conclusions. Firstly, it indicates that the vestibular system is multidimensional and that the outcome varies, dependent on what aspect of the system is targeted in a study. “Nonetheless, by now it is clear that some age-related level of decline will be measured regardless of the specific setup of a study”, Agrawal (on the picture below) comments. Her second point regards the present lack of standardization: “Nobody uses the same test, which makes it very hard to compare and aggregate data. You cannot just add up data from various tests, as they all measure something different. It is about time to change that and to come to a standard in vestibular system testing; this work is ongoing.”

Agrawal strives for such a standardized test procedure within the framework of the Bárány Society, the International Society for Neuro-Otology, of which she is a member. “There is awareness that standardization is required with regard to the future research agenda. What are the right diagnostic tests to use, given the fact that the vestibular system is closely interrelated with several organs and systems? How can we measure the condition of the vestibular system, isolated from those other systems? Wider collaboration in diagnostic testing and statistical methodology will bring us much further in understanding this problem.”

Apart from collaboration between neuro-otology specialists from all over the world, also local collaboration between various specialists, all from their own particular perspective, can be very beneficial. “It is a multifactorial system for which an integrated approach is needed. Here at Johns Hopkins, we already have set up multidisciplinary collaboration between the various relevant specialists such as neurologists, geriatrics, psychotherapists, otolaryngologists, physiotherapists and occupational therapists. We videotape the patient and evaluate the results in a multidisciplinary team. This proves very helpful to the patient.”

Intervention and prevention

As the widespread prevalence of vestibular loss only now begins to become clear and it since only recently has begun to be characterized, intervention options are still only limited. Agrawal: “The specific cases of Meniere’s, BPPV and vestibular neuritis should be diagnosed and treated. We know that in cases of vestibular migraine a migraine diet can help. But potential interventions for vestibular loss that occurs with age largely consist of vestibular therapy at this time. We are still learning and developing other potential treatments. The first step in this direction is to accurately characterize the deficit and the associated impacts, while taking other deficits into account.”

Whereas treatment is still hardly entering a pioneering phase, knowledge on prevention is already available. Agrawal: “As vestibular loss is clearly general health related, there are probably dietary factors. Apart from that, exercise is probably beneficial. An article based on a randomized controlled trial was published in the New England Journal of Medicine went into the positive preventive results of tai-chi. Participants practicing tai-chi show a significantly lower fall risk.”

Awareness

Agrawal is very happy with the fact that the Academic Research Conference chose vestibular loss as the central theme of this year's edition. “What we need is public awareness for this problem. The publicity generated by the ARC and Audiology NOW! Is certainly helpful in that respect. There is also an urgent need for collaboration, both within the specialization of neuro-otology and on a multidisciplinary level within the same clinic. In this nascent field there isn't a whole lot of guidance yet, but we are now coming at a point where guidance is needed to be able to push ahead. I certainly hope the podium for this subject in San Antonio will contribute to that.

Yuri Agrawal and the Academic Research Conference

Yuri Agrawal presented a keynote lecture entitled 'Epidemiology of Age-Related Vestibular Loss' during the Academy Research Conference (ARC) on Vestibular Assessment & Rehabilitation on March 25, 2015 preceding Audiology NOW! 2015 in San Antonio, Texas. Yuri Agrawal is Assistant Professor in the Department of Otolaryngology at Johns Hopkins University School of Medicine in Baltimore, Maryland, USA. Her clinical practice is dedicated to the medical and surgical treatment of otologic and neurotologic conditions. Her research is focused on the inner ear balance system, the vestibular system. She focuses on how the function of the vestibular system changes with aging. She is particularly interested in how age-related changes in vestibular function influence mobility, disability and fall risk in older people.

Leendert van der Ent, editor in chief of Audiology Infos The Netherlands

Photos: Wikipedia Commons / Y.A.