Pure Presbycusis and Easter Island

Easter Island has long been a destination for those that have a spirit to travel to distant places and to visit remarkable historical areas.

Easter Island is one such very remote place that is located roughly half easterway easter6between Tahiti and Chile – 2,337 miles (3,600 km) to the west of Chile, to be precise. The Island was discovered on Easter Sunday, 1722 by the Dutch explorer Jacob Roggeveen.  This small, triangular land mass is  the most isolated inhabited island in the world and home to gigantic “moai” statues carved from volcanic rock that have amazed scientists and other visitors alike throughout time. The discovery of Easter Island has an interesting history.  In 1675,  Arend Roggeveen, an  accomplished Dutch scholar and educator in mathematics, astronomy, and  navigational theory, obtained a charter from the States-General of the United  Netherlands for a South Sea venture. He and his associates, however, were  unable to obtain financial backing for it.  Arend died in 1679, but his dream  lived on in his sons, Jacob and Jan.  For  much of his life, Jacob Roggeveen was involved in religious controversy. His  professional titles included notary of Middleburg (a province capital), doctor  of law, and Council of Justice member in Batavia (today’s

easter3Jakarta in Indonesia)  of the Dutch East India Company.  He was a wealthy man when he returned to Middleburg from the Dutch East Indies in 1714, but was soon banned from the town when he resumed his support for liberal  theological doctrines.

In 1721, at age sixty-two, Roggeveen approached  the Dutch West India Company to propose making an exploratory voyage to the  unknown regions of the Pacific Ocean, which were within the boundaries defined  in the company’s charter—essentially reviving his father’s project. Jacob’s  proposal was promoted by his brother, Jan, a Middleburg merchant, who helped in  the planning and preparation after it was approved.

Departing  in August 1721, Roggeveen guided his expedition to the Falkland Islands,  through Le Maire Strait, and around easter4Cape Horn. The ships proceeded up the coast  of Chile; from February 24 until March 17, 1722, they anchored in the Juan Fernández Islands, cleaning, repairing, and resupplying in anticipation of the push into the unknown parts  of the Pacific Ocean. From there, on a west-northwest course, they sailed for  more than 1,500 miles before, on Easter Sunday (April 5), they sighted what  they hoped was the coastline of the fabled Southland: it was Easter Island.

More by accident than by design, people first discovered the islands of the South Pacific by  sailing or drifting from Southeast Asia. The first islands to be settled are those immediately to the east of New Guinea and Australia – the region called Melanesia, because of the dark skins of the inhabitants (from the Greek melas black and nesos island). The pottery of the early settlers links them with the people of the Moluccas.

Around 1300 BC, seafarers took the longest step so far in this process and reachedc Fiji, a group of islands intermediate between Melanesia and Polynesia.  It is presumed that human presence began circa 700-1100 AD, coming from the Marquesas Islands (French Polynesia, “Tahiti”),   The first staging posts were Tonga and Samoa.  The oldest surviving traces of human occupation in these islands date from about 420 BC in Tonga and 200 BC in Samoa. But it is likely that settlers arrived considerably earlier than this, since by the 1st century BC humans had reached the much more inaccessible Marquesas Islands.  The final thrust, to the most remote island groups of the Pacific, came from the Marquesas. Hawaii was reached  about AD 400; Easter Island perhaps a century later; Tahiti and the Society Islands in about 600.

SO…..

What does that have to do with hearing loss or Audiology?    

In audiology and otolaryngology there has been a continued search for “pure presbycusis”.  Of course, finding a population cin which easter10hearing loss is due solely to aging is a bit like searching for the “Holy Grail”.   Virtually everywhere hearing loss is caused at least in part by noise exposure, especially in developed societies where industry, recreation, or simply the noise of everyday life (traffic, society, etc.), lead to hearing loss that is sometimes called “sociocusis”.  The influence of noise exposure or disease, and other complicating factors have long polluted the audiometric data obtained by audiologists on older people searching for what could be called pure presbycusis. Other factors, according to Hall and Mills, 2005, such as genetic susceptibility, age-related diseases, and ototoxic medication, can add to the burden, but not necessarily in a linear manner.

Last fall, in a Hearing International discussion of stem cell research, we touched on “pure presbycusis” and the quest to determine just how much hearing loss is due to aging and how much is from noise exposure and other factors.  Rosen et al., in their classic studies from the 1960s on the Mabaan Tribe in Sudan, reported by Bergman (1966), shed much light on this issue and remains one of the most authoritative discussions of pure presbycusis.

Another study, less publicized than the Mabaan Tribe data, comes from Easter Island. Evidence that societal noise contributes to presbycusis there is offered by Goycoolea et al, 1986. To determine if life in industrialized societies can affect hearing, Goycoolea and colleagues evaluated 90 natives from Easter Island over 45 years old. These easter11subjects underwent complete clinical and audiological assessment and were then divided into groups according to whether they had lived only on the island or whether they had lived for a time in a more modern place. With all factors being equal, except exposure to the noise of modern civilization, the results of the study demonstrated that living in modern societies has a significant negative effect on hearing, and that the the severity  of hearing loss is directly proportional to the years of exposure. The median hearing thresholds of natives who had always lived on the island (men and women combined) were found to be similar to those of female citizens of the United States. There was no significant difference in hearing thresholds between men and women among these natives.

These results suggest that there are no significant inherent racial differences nor significant inherent differences between males and females in the sensitivity of hearing. A relationship between aging and hearing was noted and interpreted as true, intrinsic or “pure presbycusis.”  No cases of otosclerosis, Meniere’s disease, or exostoses of the external ear canal  were discovered among natives who had always lived on the island.  These people were found not to be prone to otitis media despite having an extremely high incidence of severe upper respiratory tract allergies.  Levy and her colleagues point to past studies that found lower rates of age-related hearing loss in cultures that place less stigma on getting older. Research has found, for example, that older residents of Easter Island, where the elderly are seen in a positive light, have less hearing loss than older adults who had left the island for industrialized nations.easter11.jpg

So….did these researchers find the “Holy Grail” of pure presbycusis on Easter Island?  Although not totally conclusive, it appears that the combination of Dr. Rosen’s data in the 1960s and the further research of this isolated population suggests that there is a pure aging component to hearing loss but that our environment tends to  significantly accelerate the hearing loss process. As depicted in Monty Python and the Holy Grail, our environment is a bit like the “holy hand grenade” to our hearing. (Click here for a fun scene from that movie “Holy Grail”)

About Robert Traynor

Robert M. Traynor, Ed.D., MBA is the CEO and practicing audiologist at Audiology Associates, Inc., in Greeley, Colorado with particular emphasis in amplification and operative monitoring, offering all general audiological services to patients of all ages. Dr. Traynor holds degrees from the University of Northern Colorado (BA, 1972, MA 1973, Ed.D., 1975), the University of Phoenix (MBA, 2006) as well as Post Doctoral Study at Northwestern University (1984). He taught Audiology at the University of Northern Colorado (1973-1982), University of Arkansas for Medical Sciences (1976-77) and Colorado State University (1982-1993). Dr. Traynor is a retired Lt. Colonel from the US Army Reserve Medical Service Corps and currently serves as an Adjunct Professor of Audiology at the University of Florida, the University of Colorado, and the University of Northern Colorado. For 17 years he was Senior International Audiology Consultant to a major hearing instrument manufacturer traveling all over the world providing academic audiological and product orientation for distributors and staff. A clinician and practice manager for over 35 years, Dr. Traynor has lectured on most aspects of the field of Audiology in over 40 countries. Dr. Traynor is the current President of the Colorado Academy of Audiology and co-author of Strategic Practice Management a text used in most universities to train audiologists in practice management, now being updated to a 2nd edition.