Dementia: Tactile decline may signal early cognitive impairment

A new scientific review published in Biological Psychology highlights the potential role of touch-related sensory decline as an early warning sign for cognitive deterioration. The findings suggest that age-related impairments in tactile perception — including sensitivity to pressure, vibration, and object recognition — may predict cognitive challenges and even the progression toward dementia. The review outlines how changes in the brain’s sensory processing areas, especially the hippocampus, are tightly linked to both declining touch perception and memory, attention, and executive functioning.

The researchers conducted this review to better understand how age-related sensory decline, particularly in the tactile system, could be a harbinger of cognitive impairment. As global populations continue to live longer, mild cognitive impairment is becoming more common, affecting roughly one in six older adults.

In many cases, this condition progresses to dementia. Identifying early markers of decline can help delay or prevent more serious outcomes. Since most people experience some level of tactile deterioration as they age, the authors wanted to explore whether this decline could provide an early and accessible signal of future cognitive problems.

To explore this question, the research team examined previous studies that analyzed tactile deterioration across the aging brain. They reviewed evidence from human studies as well as animal models, especially in rodents, which allowed researchers to isolate and manipulate tactile input through experimental methods.

Across this body of literature, the authors looked for connections between loss of tactile function, brain changes, and cognitive outcomes. They paid special attention to the hippocampus and its links to tactile input, spatial memory, and executive function. The review also included structural imaging studies and behavioral assessments, giving a comprehensive overview of how sensory decline and cognitive decline might unfold together.

The review begins by outlining the gradual decline of the tactile system with age. As early as age 20, touch sensitivity begins to decrease, and by age 60, these changes can be clinically detected. Mechanoreceptors in the skin, particularly Meissner’s and Pacinian corpuscles that detect fine touch and vibration, begin to disappear. The nerves that transmit tactile information lose some of their insulating material, which slows signal transmission.

These changes affect not just the skin but also the spinal cord and brain, particularly the primary somatosensory cortex, which becomes thinner with age and shows reduced inhibition. This results in poorer touch discrimination, difficulty in manipulating objects, reduced fine motor control, and problems with balance.

The researchers then connected these sensory changes to cognitive decline, particularly in the context of mild cognitive impairment. This condition is defined as a decline in mental functioning that goes beyond normal aging but does not yet interfere significantly with daily activities. It is often a precursor to dementia. Studies show that mild cognitive impairment is more common with increasing age, affecting over one-quarter of people aged 80 or older. Importantly, over a third of these individuals eventually develop dementia. Understanding what triggers this progression is key to prevention.

According to the review, one of the earliest areas of the brain to show changes in mild cognitive impairment is the hippocampus, a region essential for memory, learning, and executive functioning. The hippocampus receives sensory input from the somatosensory system via the entorhinal cortex. Tactile input helps the hippocampus integrate information and support cognitive flexibility and decision-making.

When this input is diminished due to aging or sensory deprivation, hippocampal function may suffer. For instance, studies in rodents show that depriving animals of tactile input through whisker removal reduces hippocampal activity, impairs spatial memory, and disrupts synaptic communication in memory-related regions.

In one type of experiment, researchers permanently removed the whiskers of rodents, which serve as their primary tactile system. These animals showed significantly less brain activity in the hippocampus, reduced formation of new neurons, and problems with navigation and object recognition. In contrast, stimulating the whiskers increased dopamine levels in the hippocampus and improved memory performance. These findings mirror what has been observed in human studies, where reduced tactile stimulation can lead to poorer cognitive outcomes, while tactile engagement can improve memory and attention.

The review also highlights proprioception — the sense of body position and movement — and stereognosis — the ability to recognize objects through touch — as key components of the tactile system that are affected by aging. Both are critical for daily functioning and are also linked to cognitive performance. When these abilities decline, individuals may experience increased risk of falls, reduced independence, and fewer opportunities for cognitive engagement. This drop in activity and stimulation can, in turn, accelerate cognitive deterioration.

One of the more compelling findings discussed in the review is the link between tactile impairments and changes in the neurochemistry of the brain. Sensory stimulation boosts levels of acetylcholine, a chemical that plays a major role in attention and memory. It also promotes the release of brain-derived neurotrophic factor (BDNF) and fibroblast growth factor (FGF-2), both of which help support the growth and survival of neurons. Tactile deprivation, by contrast, lowers these factors, potentially triggering cell death and weakening memory circuits in the hippocampus.

The authors propose that this body of evidence supports the idea that tactile deterioration may be more than just a sign of aging — it could be an early marker of cognitive risk. If so, touch-based assessments could become a valuable tool in detecting people who may benefit from early intervention. This is especially important because many traditional cognitive screening tools may miss early signs, or may not be accessible to all populations.

The review suggests several directions for future research. One recommendation is to develop standardized methods for measuring tactile function, including proprioception and stereognosis, in older adults. These assessments could be added to routine cognitive screenings. Another area for exploration is whether tactile-based interventions — such as textured objects, massage therapy, or sensory-rich environments — can help protect or even restore cognitive function.

The authors also encourage more research into how different sensory systems interact and contribute to overall cognitive health, including studies that combine touch, sound, and visual stimulation to promote brain plasticity.

The paper, “The role of tactile sense as an early indicator of cognitive decline in aging,” was authored by Nereida Ibarra-Castaneda, Adriana Gonzalez-De-la-Cerda, and Oscar Gonzalez-Perez.