This week, I am analyzing the science behind an article in the U.S. News & World Report titled "Diminished Hearing, Vision Together Could Be Risk Factor for Dementia."
Summary of Article:
The article reports on the findings of a recent South Korean study that found that a "combination of hearing and vision loss is tied to an increased risk of mental decline and dementia", although just losing one or the other does not have a correlation with dementia. The possible explanation is, according to Dr. Jin Hyeong Woo, that older people with only vision or hearing loss may not "feel as isolated or depressed" compared to people with both vision and hearing loss. People that lose both vision and hearing are unable to maintain social contact as easily, and subsequently are more likely to develop depression, which is associated with dementia. In a study involving 6520 participants between 58-101 years of age, researchers discovered that "people with both hearing and vision impairment were twice as likely to develop dementia as those with one or neither of the impairments." One US expert Dr. Darius Kohan finds the study weakened by the fact that it "relied on people's self-reports of vision or hearing loss." Furthermore, it is unclear if the results can be generalized outside of Korea to non-Korean populations. Another interesting point to consider is that US and worldwide researchers have found a correlation between hearing loss alone and dementia, associated with "isolation, diminished communication and withdrawal from interacting with others, leading to disproportional cognitive decline."
Science Behind Article:
The news article did not cite the South Korean study it discusses, and I also could not find the study in question through a Google search. After looking up Dr. Jin Hyeong Woo, however, I found that he has published other articles about dementia, lending to his credibility. Dr. Darius Kohan is a leading ear specialist in New York City, so his remark that hearing loss alone is associated with dementia seems credible. One scientific article I found that is relevant to the news article is called "Is Depression a Risk Factor for Dementia or Cognitive Decline?" by Jorm A.F. The study found that "There is sufficient evidence to take seriously the possibility that depression is a risk factor for dementia and cognitive decline." This finding is in line with the remarks by Dr. Jin Hyeong Woo that were cited in the news article with regard to increased depression and an association with higher risk of dementia.
Another scientific article I found that is related to the news article is titled, "Association of Hearing Loss With Dementia" by Chin-Mei Liu, PhD and Charles Tzu-Chi Lee, PhD. In this Taiwanese study, scientists found that "hearing loss was positively associated with dementia, especially in patients aged 45 to 64 years." Although this finding is inconsistent with the study that the news article reported on, which found that both hearing loss and vision loss together were associated with dementia but not either alone, the news article did acknowledge that there are studies which found that hearing loss alone is associated with dementia. Therefore, the results of this scientific study are also in line with the science discussed in this news article.
Finally, a third scientific article I found that is relevant to the news article is titled "Dual sensory impairment in older adults and risk of dementia from the GEM Study" by Phillip H. Hwang et al. This study found that in following up on 11,392 participants, "321 participants (15.6%) developed all‐cause dementia: 14.3% in participants with no sensory impairments, 16.9% in those with one sensory impairment, and 28.8% in those with DSI." These results are similar to those of the South Korean study in question in the news article, which reported that "dementia was more than twice as common among people with both impairments (8%) than among those with one impairment (2.4%) or neither impairment (2.3%)." In both studies, the association between hearing loss alone and dementia was not as significant as the association between dual sensory loss and dementia, which suggests that the study reported on by the news article is not necessarily in the wrong, although it does contradict many other studies that have found a link between hearing loss alone and dementia.
Assessment: Was Science Misused?
Overall, I think that this news article did not misuse the science and reported the science behind the relationship between sensory loss and dementia accurately. The news article especially did a good job in acknowledging possible disagreement within the scientific community regarding whether dual sensory loss is more significantly correlated with dementia than hearing loss alone. I do think it is rather interesting, though, why this news article chose to conclude with the statement from Dr. Kohan that US and worldwide studies found a link between hearing loss alone and dementia, and thus casting some doubt on the findings of this South Korean study. Especially considering how another study found a very similar significant correlation between dual sensory loss and dementia as compared to either vision or hearing loss alone and dementia, I think it is interesting how the numbers show a clearly significant difference in rates of dementia between people with both impairments compared to people with only one impairment. I wonder if there may be some bias for US findings compared to non-US findings. Ultimately though, the U.S. News & World Report presented the findings of this study accurately and did a pretty good job of discussing the various viewpoints, although with a possible bias toward the US over South Korea.
Thanks for reading!
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