A diminishment of both hearing and vision is linked to an increased risk for dementia and mental decline, according to a new study.
Published online in the April 7 issue of Neurology, the South Korean study found that having just one of the two impairments is not connected with a higher risk.1
The study consisted of 6,520 participants between ages 58 and 101, with visual and hearing impairments assessed by a questionnaire asking about their use of glasses or hearing aids.
Of those individuals, 932 people reported having both normal vision and hearing, 2,957 claimed either visual or hearing issues, and 2,631 said they had both impairments.
At the beginning of the study, dementia was more than twice as common in the group with both impairments. From that, 8% had the disease at the start, compared to 2.4% in the group with one sensory impairment and 2.3% with no sensory impairment.
Participants’ thinking and memory skills were evaluated every 2 years for 6 years via a wood recall and recognition test. Researchers then assessed the relationship between having one sensory impairment and dementia, as well as having both impairments and dementia.
Throughout this 6-year follow-up period, 245 participants developed dementia.
Further, from the 1,964 individuals with both hearing and vision impairment: 146 developed dementia; 69 of the 2,397 individuals with one impairment developed dementia; 14 of the 737 individuals with no impairments developed dementia; and 16 out of the 142 individuals who could not determine if they had a sensory impairment also developed dementia.1
Upon adjustment for various factors — sex, education, income — investigators discovered the group with both hearing and vision impairments were twice as likely to develop dementia compared to the group with normal hearing and vision. Participants with only one impairment were found to be no more likely to develop dementia as the group with normal sensory function.1
Further, the decrease in scoring on the thinking test was higher among those with both a hearing and vision impairment.
While it is not apparent why a decline in both senses — not just one — may raise the risk for dementia, investigators theorized the importance of socialization as being key to a mentally sharp mind.
"Older people with only a visual or hearing impairment can usually still maintain social contact, so they may not feel as isolated or depressed as people who have both impairments," said Dr. Jin Hyeong Jhoo of Kangwon National University School of Medicine in Chuncheon, South Korea, in an American Academy of Neurology article.
However, Dr. Jhoo further explained, when an individual has both impairments, their risk of isolation and depression may also increase.
Jhoo stated that additional research would be needed to explain why those with two impairments are at a greater risk for developing dementia than those with just one impairment.
To note, a drawback of this study included the self-reports of participants on the distributed questionnaire.
1. Gihwan B, Gyu han Oh, Jin Hyeong Jhoo, Jae-Won Jang, Jong Bin Bae, Ji Won Han, Tae Hui Kim, Kyung Phil Kwak, Bong Jo Kim, Shin Gyeom Kim, Jeong Lan Kim, Seok Woo Moon, Joon Hyuk Park, Seung-Ho Ryu, Jong Chul Youn, Dong Woo Lee, Seok Bum Lee, Jung Jae Lee, Dong Young Lee, Ki Woong Kim. Dual Sensory Impairment and Cognitive Impairment in the Korean Longitudinal Elderly Cohort. Neurology. Apr 2021, 10.1212/WNL.0000000000011845; DOI: 10.1212/WNL.0000000000011845