How Many Deaf People in the World Today? Origins of the Global Hearing Loss Prevalence Figures
P.W. Alberti, MBBS, PhD, FRCS Professor Emeritus, ORL, University of Toronto, and Ex-General Secretary, International Federation of Otolaryngological Societies In 1974, Sir John Wilson, a charismatic blind British activist, founded the World Health Organization (WHO) Global Prevention of Blindness program. A decade later, he challenged otolaryngology and audiology to do the same for hearing loss (HL). WHO had ignored hearing loss but, under the leadership of Baron Jean E. F. Marquet of Antwerp, Belgium, the International Society of Audiology (ISA) and the International Federation of Otolaryngological Societies (IFOS) conducted intense lobbying. In 1986, this led WHO to commission an internal report on prevalence of HL. Based on a 1971 U.S. public health survey, the report concluded that 42 million people worldwide suffered from moderate to severe HL. WHO initiated a Prevention of Deafness and Hearing Loss program (PDH), but unfortunately because of low prevalence, it was not funded. However, the figure of 42 million was greeted with incredulity—the landmark UK audiometric prevalence study by Davis, et al., had found a much higher prevalence. In fact, the WHO study probably had a transcription error, perhaps related to differing definitions of zero dB in the U.S. and ISO standards at that time. In 1991, PDH was placed in the Prevention of Blindness program under the excellent leadership of its director, Bjorn Thylefors, MD. One of his first actions was to host a weeklong external consultation, at which James B. Snow Jr., MD, played a pivotal role, setting the PDH program to the present time. Spurred by the urgent need to update the prevalence figures, Jun-Ichi Suzuki, MD, seconded from Japan to WHO for a year, developed the underpinnings of later national surveys conducted by and with WHO. In 1994, after surveying literature from the Liverpool School of Tropical Medicine’s Kenneth W. Newell collection, I produced a conservative estimate of 150 million worldwide. To avoid exaggeration, the WHO unilaterally cut this figure to 120 million worldwide. When presented to the 1995 WHO General Assembly, this figure led to a resolution urging action on HL, because of the apparent increase in prevalence. Andrew W. Smith, MSc, MRCP, hired from Liverpool and funded by CBM (Christian Blind Mission), initiated many regional and national surveys. With limited resources, however, these surveys were still too few. The Chinese (PRC) national disability survey of the 1980s showed HL complaints of only 1.7 percent, which dragged down the global figures. Only in the 21st century did the PRC undertake a representative audiometric study that shows prevalence about four percent, similar to the rest of the world. Meanwhile the aging global population grew by more than one billion. WHO undertook an internal study proposing a HL prevalence of 235 million. The global burden of disease (GBD), initially a WHO initiative, was revised and lowered the threshold for disabling hearing loss to >34 dB. WHO then raised the prevalence, at >34 dB, to 500 million, although not yet accepting the changed definition. Even at that threshold, GBD concluded the prevalence was only 235 million. The discrepancy remains unresolved.
P.W. Alberti, MBBS, PhD, FRCS
Professor Emeritus, ORL, University of Toronto, and Ex-General Secretary, International Federation of Otolaryngological Societies
In 1974, Sir John Wilson, a charismatic blind British activist, founded the World Health Organization (WHO) Global Prevention of Blindness program. A decade later, he challenged otolaryngology and audiology to do the same for hearing loss (HL). WHO had ignored hearing loss but, under the leadership of Baron Jean E. F. Marquet of Antwerp, Belgium, the International Society of Audiology (ISA) and the International Federation of Otolaryngological Societies (IFOS) conducted intense lobbying.
In 1986, this led WHO to commission an internal report on prevalence of HL. Based on a 1971 U.S. public health survey, the report concluded that 42 million people worldwide suffered from moderate to severe HL. WHO initiated a Prevention of Deafness and Hearing Loss program (PDH), but unfortunately because of low prevalence, it was not funded.
However, the figure of 42 million was greeted with incredulity—the landmark UK audiometric prevalence study by Davis, et al., had found a much higher prevalence. In fact, the WHO study probably had a transcription error, perhaps related to differing definitions of zero dB in the U.S. and ISO standards at that time.
In 1991, PDH was placed in the Prevention of Blindness program under the excellent leadership of its director, Bjorn Thylefors, MD. One of his first actions was to host a weeklong external consultation, at which James B. Snow Jr., MD, played a pivotal role, setting the PDH program to the present time. Spurred by the urgent need to update the prevalence figures, Jun-Ichi Suzuki, MD, seconded from Japan to WHO for a year, developed the underpinnings of later national surveys conducted by and with WHO.
In 1994, after surveying literature from the Liverpool School of Tropical Medicine’s Kenneth W. Newell collection, I produced a conservative estimate of 150 million worldwide. To avoid exaggeration, the WHO unilaterally cut this figure to 120 million worldwide. When presented to the 1995 WHO General Assembly, this figure led to a resolution urging action on HL, because of the apparent increase in prevalence.
Andrew W. Smith, MSc, MRCP, hired from Liverpool and funded by CBM (Christian Blind Mission), initiated many regional and national surveys. With limited resources, however, these surveys were still too few. The Chinese (PRC) national disability survey of the 1980s showed HL complaints of only 1.7 percent, which dragged down the global figures. Only in the 21st century did the PRC undertake a representative audiometric study that shows prevalence about four percent, similar to the rest of the world.
Meanwhile the aging global population grew by more than one billion. WHO undertook an internal study proposing a HL prevalence of 235 million. The global burden of disease (GBD), initially a WHO initiative, was revised and lowered the threshold for disabling hearing loss to >34 dB. WHO then raised the prevalence, at >34 dB, to 500 million, although not yet accepting the changed definition. Even at that threshold, GBD concluded the prevalence was only 235 million. The discrepancy remains unresolved.