The National Institutes of Health reports that the United States’ population is older today than it has ever been. As the number of older people is projected to nearly double over the next three decades, so grows the importance of research highlighting the intersections among sensory impairments, overall health and quality of life in this group.

A new Johns Hopkins Medicine study, published Jan. 18 in JAMA Otolaryngology–Head and Neck Surgery, suggests that the number and severity of sensory impairments are strongly tied to decreased physical functioning and increased mortality risk. The study's primary goal was to understand how types and numbers of sensory deficits in areas such as vision, hearing, smell and touch affect physical functioning and the risk of mortality among older adults.

“Challenges with balance, difficulty in distinguishing contrasts, a reduced ability to identify smells and difficulty hearing in noisy environments may all be warning signs,” says researcher Varun Vohra. “These sensory impairments can lead to a decline in physical function, such as slower walking speed, trouble with daily activities like climbing stairs or standing from a seated position, and could potentially increase the risk of accidents, social isolation and overall decline in quality of life.”

To examine the relationship between multiple sensory deficits and overall health and longevity for older adults, the research team analyzed data from more than 3,000 older adults as part of the Health, Aging and Body Composition (Health ABC) study from 1997 to 2013. The seniors were aged between 70 to 79 years. The mean age was 77 years, and 52% of study participants were female.

Researchers evaluated the participants’ visual, olfactory, auditory and touch sensory functions from 2000 and 2002, and then monitored the participants over the years using the Health ABC physical performance battery (HABCPPB). The HABCPPB measures physical performance using four components: usual gait speed, time to stand up from and sit back down on an armless chair five times, ability to hold three balance-related stances for up to thirty seconds each, and ability and time to walk a narrow 6-meter course. Overall, the HABCPPB score constitutes the sum of these four ratio scores, with scores ranging from 0 (poor performance) to 4 (excellent performance).

A clear pattern emerged: The more sensory impairments a person had, the more rapid the decline in their physical functioning. Specifically, having between one and four sensory impairments was associated with lower HABCPPB scores and progressively steeper declines in physical function. Participants with four sensory impairments declined at a rate four times faster than those with one impairment.

The risk of mortality also increased with the number of sensory impairments. Relative to participants with no impairments, those with one severe sensory impairment had a 32% increased risk of mortality over 10 years. This figure grew to 64% with two severe impairments and a staggering 126% with three or more impairments.

Researchers say multisensory impairment may be a contributor to a cascade of health declines or a signal of underlying health issues. This may lead to the theorized “point of no return,” in which an older adult’s decline becomes irreversible.

However, researchers emphasize that sensory impairments are not an inevitable and unmanageable part of aging. As study results also indicate that a lower number of sensory impairments is associated with improved health status and resilience, early screening, prevention and treatment of sensory impairments could be key strategies in reducing health risks and improving the aging population’s quality of life.

“While the study finds an association between sensory impairments and negative health outcomes, this does not mean that all individuals will experience these impairments or that they cannot be mitigated,” Vohra says. “It’s also important to avoid the determinist view that sensory impairments directly cause mortality without considering the role of comorbidities and other factors.”

Study findings suggest interventions such as hearing aids and olfactory training may mitigate the impact of sensory losses. By identifying impairments early, health care practitioners can offer targeted strategies to improve sensory function, which may help maintain physical function and reduce the risk of mortality.

“With appropriate screening and early intervention strategies, it is possible to identify sensory impairments early and take steps to manage them,” says Vohra. “This proactive approach could help maintain a better quality of life for older adults, slowing the progression of physical decline, possibly extending life expectancy, and enhancing the health and independence of the aging population.”

Researchers say this study opens new avenues for research, particularly regarding olfactory impairment. While there are established benefits of interventions such as hearing aids and glasses and protective measures against falls for those with diminished tactile senses, the impact of the loss of smell is a relatively unexplored area despite its unique association with life span and mortality.

“This study highlights the importance of further investigating how and why the sense of smell can be assessed in older adults,” says Nicholas Rowan, associate professor of otolaryngology–head and neck surgery and corresponding author of the study. “Moreover, the potential impact of smell-focused therapies on health span and life span offers potential new and exciting opportunities aimed at improving longevity.”

Rowan and his colleagues from the Johns Hopkins University Claude D. Pepper Older Americans Independence Center are investigating how more detailed smell tests may help researchers and clinicians identify older adults who are physiologically vulnerable.

Other researchers involved in this study include Yuri Agrawal, Eleanor Simonsick, Vidyulata Kamath and Karen Bandeen-Roche.

Funding from this study was supported by the Johns Hopkins University Claude D. Pepper Older Americans Independence Center, the National Institute on Aging and the National Institutes of Health.

No authors report conflict of interest.