Somatosensory function in old age

Somatosensory Amplification Scale-Chinese version: psychometric properties and its mediating role in the relationship between alexithymia and somatization

The Somatosensory Amplification Scale (SSAS) was designed to measure individual's tendency to experience visceral and somatic sensations as unusually intense, disturbing and alarming. In this study, we aimed to investigate the reliability and validity of the SSAS in the Chinese general population, as well as the mediating effect of somatosensory amplification in the relationship between alexithymia and somatization. A total of 386 healthy adults were enrolled in this study. Participants completed the Chinese versions of the Somatosensory Amplification Scale (SSAS-C), the somatization subscale of the Symptom Check List 90 (SCL-90 som), the Toronto Alexithymia Scale (TAS-20), and the Short form Health Anxiety Inventory (SHAI). One hundred and thirty-three participants were randomly selected to complete the SSAS-C again two weeks after the initial assessment. The reliability and validity of the SSAS-C were analyzed. Confirmatory factor analysis showed that the one-factor model achieved adequate model fits; one item was deleted due to low factor loading. The revised SSAS-C showed good internal consistency and test-retest reliability. The SSAS-C scores correlated positively with the scores of SCL-90 som, TAS-20 and the SHAI, showing good convergent validity. In addition, somatosensory amplification mediated the association between alexithymia and somatization. The Chinese version of SSAS has acceptable reliability and validity for the general population. In addition, alexithymia may increase somatization through higher somatosensory amplification.

Sensational Dreams: The Prevalence of Sensory Experiences in Dreaming

Dreaming, a widely researched aspect of sleep, often mirrors waking-life experiences. Despite the prevalence of sensory perception during wakefulness, sensory experiences in dreams remain relatively unexplored. Free recall dream reports, where individuals describe their dreams freely, may not fully capture sensory dream experiences. In this study, we developed a dream diary with direct questions about sensory dream experiences. Participants reported sensory experiences in their dreams upon awakening, over multiple days, in a home-based setting (n = 3476 diaries). Our findings show that vision was the most common sensory dream experience, followed by audition and touch. Olfaction and gustation were reported at equally low rates. Multisensory dreams were far more prevalent than unisensory dreams. Additionally, the prevalence of sensory dream experiences varied across emotionally positive and negative dreams. A positive relationship was found between on the one hand sensory richness and, on the other emotional intensity of dreams and clarity of dream recall, for both positive and negative dreams. These results underscore the variety of dream experiences and suggest a link between sensory richness, emotional content and dream recall clarity. Systematic registration of sensory dream experiences offers valuable insights into dream manifestation, aiding the understanding of sleep-related memory consolidation and other aspects of sleep-related information processing.

Age-associated changes in multimodal pain perception

BACKGROUND

Pain sensitivity varies across multimodal somatosensory stimuli that can rely on different conductive fibres, which, when damaged, will lead to neuropathies. However, there is limited research examining the characteristics of perceived pain, particularly as affected by the ageing process, as induced by various somatosensory stimuli that may rely on small or large fibres.

METHODS

Using heat and pressure stimuli on small and large fibres separately on both younger and older adults, this study examined age-associated changes in pain perception by measuring self-reported pain sensitivity, pain threshold and pain discriminability.

RESULTS

Heat pain threshold was significantly positively correlated with age, but not pressure pain threshold. Pain threshold increased and pain discriminability decreased in response to heat stimuli in the older participants compared with the younger ones.

CONCLUSION

An age-associated decline in heat pain perception was observed, suggesting an earlier degradation of heat perception. These findings provide new insight into understanding and assessing somatosensory disorders, which can help ageing populations better maintain healthy sensory functioning.

Worldwide cohort studies to support healthy ageing research: data availabilities and gaps

BACKGROUND

Population ageing is a transforming demographic force. To support evidence-based efforts for promoting healthy ageing, a summary of data availabilities and gaps to study ageing is needed.

METHOD

Through a multifaceted search strategy, we identified relevant cohort studies worldwide to studying ageing and provided a summary of available pertinent measurements. Following the World Health Organization's definition of healthy ageing, we extracted information on intrinsic capacity domains and sociodemographic, social, and environmental factors.

RESULTS

We identified 287 cohort studies. South America, the Middle East, and Africa had a limited number of cohort studies to study ageing compared to Europe, Oceania, Asia, and North America. Data availabilities of different measures varied substantially by location and study aim. Using the information collected, we developed a web-based Healthy Ageing Toolkit to facilitate healthy ageing research.

CONCLUSIONS

The comprehensive summary of data availability enables timely evidence to contribute to the United Nations Decades of Healthy Ageing goals of promoting healthy ageing for all. Highlighted gaps guide strategies for increased data collection in regions with limited cohort studies. Comprehensive data, encompassing intrinsic capacity and various sociodemographic, social, and environmental factors, is crucial for advancing our understanding of healthy ageing and its underlying pathways.

Aging exerts a limited influence on the perception of self-generated and externally generated touch

Touch generated by our voluntary movements is attenuated both at the perceptual and neural levels compared with touch of the same intensity delivered to our body by another person or machine. This somatosensory attenuation phenomenon relies on the integration of somatosensory input and predictions about the somatosensory consequences of our actions. Previous studies have reported increased somatosensory attenuation in elderly people, proposing an overreliance on sensorimotor predictions to compensate for age-related declines in somatosensory perception; however, recent results have challenged this direct relationship. In a preregistered study, we used a force-discrimination task to assess whether aging increases somatosensory attenuation and whether this increase is explained by decreased somatosensory precision in elderly individuals. Although 94% of our sample (n = 108, 21-77 yr old) perceived their self-generated touches as weaker than externally generated touches of identical intensity (somatosensory attenuation) regardless of age, we did not find a significant increase in somatosensory attenuation in our elderly participants (65-77 yr old), but a trend when considering only the oldest subset (69-77 yr old). Moreover, we did not observe a significant age-related decline in somatosensory precision or a significant relationship of age with somatosensory attenuation. Together, our results suggest that aging exerts a limited influence on the perception of self-generated and externally generated touch and indicate a less direct relationship between somatosensory precision and attenuation in the elderly individuals than previously proposed.NEW & NOTEWORTHY Self-generated touch is attenuated compared with externally generated touch of identical intensity. This somatosensory attenuation has been previously shown to be increased in elderly participants, but it remains unclear whether it is related to age-related somatosensory decline. In our preregistered study, we observed a trend for increased somatosensory attenuation in our oldest participants (≥69 yr), but we found no evidence of an age-related decline in somatosensory function or a relationship of age with somatosensory attenuation.

Insulin syringe for anesthesia in ptosis surgery: a randomized, fellow eye-controlled clinical study

PURPOSE

Unlike ordinary 30-gauge needles, insulin syringe needles are thinner and shorter and have a comparatively blunt tip. Therefore, insulin syringes may reduce injection discomfort, bleeding, and edema by minimizing tissue damage and vascular penetration. This study aimed to evaluate the potential benefits of using insulin syringes for local anesthesia in ptosis surgery.

METHODS

This randomized, fellow eye-controlled study included 60 patients (120 eyelids), conducted at a university-based hospital. An insulin syringe was used on one eyelid, and a conventional 30-gauge needle was used on the other. Patients were instructed to score pain in both eyelids using a visual analog scale (VAS) ranging from 0 (no pain) to 10 (unbearable pain). Ten minutes after the injection, two observers scored degrees of hemorrhage and edema in both eyelids on five- and four-pointing grading scales (0-4 and 0-3) for each value, and the average score between the two observers was calculated and compared.

RESULTS

The VAS score was 5.17 in the insulin syringe group and 5.35 in the 30-gauge needle group (p = 0.282). Ten minutes after the anesthesia, the median hemorrhage scores were 1.00 and 1.75 (p = 0.010), and the median eyelid edema scores were 1.25 and 2.00 (p = 0.007) in the insulin syringe and 30-gauge needle groups, respectively (Fig. 1).

CONCLUSION

Injecting local anesthesia using an insulin syringe significantly reduces hemorrhage and eyelid edema, but not injection pain, before skin incision. Insulin syringes are useful in patients at high risk of bleeding because they can reduce the penetrative tissue damage caused by needle insertion.

Shrinking of spatial hand representation but not of objects across the lifespan

Perception and action are based on cerebral spatial representations of the body and the external world. However, spatial representations differ from the physical characteristics of body and external space (e.g., objects). It remains unclear whether these discrepancies are related to functional requirements of action and are shared between different spatial representations, indicating common brain processes. We hypothesized that distortions of spatial hand representation would be affected by age, sensorimotor practice and external space representation. We assessed hand representations using tactile and verbal localization tasks and quantified object representation in three age groups (20-79 yrs, total n = 60). Our results show significant shrinking of spatial hand representations (hand width) with age, unrelated to sensorimotor functions. No such shrinking occurred in spatial object representations despite some common characteristics with hand representations. Therefore, spatial properties of body representation partially share characteristics of object representation but also evolve independently across the lifespan.

Age Differences in Multimodal Quantitative Sensory Testing and Associations With Brain Volume

BACKGROUND AND OBJECTIVES

Somatosensory function is critical for successful aging. Prior studies have shown declines in somatosensory function with age; however, this may be affected by testing site, modality, and biobehavioral factors. While somatosensory function declines are associated with peripheral nervous system degradation, little is known regarding correlates with the central nervous system and brain structure in particular. The objectives of this study were to examine age-related declines in somatosensory function using innocuous and noxious stimuli, across 2 anatomical testing sites, with considerations for affect and cognitive function, and associations between somatosensory function and brain structure in older adults.

RESEARCH DESIGN AND METHODS

A cross-sectional analysis included 84 "younger" (n = 22, age range: 19-24 years) and "older" (n = 62, age range: 60-94 years) healthy adults who participated in the Neuromodulatory Examination of Pain and Mobility Across the Lifespan study. Participants were assessed on measures of somatosensory function (quantitative sensory testing), at 2 sites (metatarsal and thenar) using standardized procedures, and completed cognitive and psychological function measures and structural magnetic resonance imaging.

RESULTS

Significant age × test site interaction effects were observed for warmth detection (p = .018,η p 2 = 0.10) and heat pain thresholds (p = .014,η p 2 = 0.12). Main age effects were observed for mechanical, vibratory, cold, and warmth detection thresholds (ps < .05), with older adults displaying a loss of sensory function. Significant associations between somatosensory function and brain gray matter structure emerged in the right occipital region, the right temporal region, and the left pericallosum.

DISCUSSION AND IMPLICATIONS

Our findings indicate healthy older adults display alterations in sensory responses to innocuous and noxious stimuli compared to younger adults and, furthermore, these alterations are uniquely affected by anatomical site. These findings suggest a nonuniform decline in somatosensation in older adults, which may represent peripheral and central nervous system alterations part of aging processes.

Age-related changes in oral tactile and thermal sensation throughout adulthood

Although the life expectancy of women is over 80 years in many countries, oral sensation has scarcely been compared between adults ≥ 80 years and younger age groups. The purpose of this study was to clarify age-related changes in oral sensation throughout adulthood. After exclusion of individuals with factors that might have confounded somatosensory performance, 123 female participants were divided into four age groups: 20-39 years, 40-59 years, 60-79 years, and 80-96 years. Perceptions of tactile and thermal sensations were examined at points on the anterior and posterior palate, anterior and posterior tongue, lower labial-attached gingiva, lower lip, and buccal mucosa; two-point discrimination was examined only on the tongue. The tactile and two-point discrimination thresholds for the anterior and posterior tongue were significantly higher in the 80-96-year-old group than in any other age group (p < 0.05). The tactile threshold for the buccal mucosa was significantly higher in the 80-96-year-old group than in the 60-79-year-old group (p < 0.05). The percentage of participants able to perceive a warm stimulus (50 °C) in the buccal mucosa was significantly lower in the 80-96-year-old group than in the 20-39-year-old group (p < 0.05). Only the topography of the warm sensation perception changed with age. This cross-sectional study suggests that oral tactile and thermal sensation for warm stimuli deteriorates with age in a site-specific manner, especially after the age of 80 years, but the same does not occur with cool stimuli.

Time for a Systems Biological Approach to Cognitive Aging?-A Critical Review

The underlying premise of current theories of cognitive decline with age tend to be primarily cognitive or biological explanations, with relatively few theories adequately integrating both aspects. Though literature has also emphasized the importance of several factors that contribute to cognitive aging including: (a) decline in sensory abilities; (b) the effect of motor speed on paper-pencil measures of cognitive speed; (c) the impact of level of education and physical activity; and (d) molecular biological changes that occur with age, these factors have seldom been implicated into any single theoretical model of cognitive aging. Indeed, such an integrated bio-cognitive model of aging has the potential to provide a more comprehensive understanding of attention, perception, learning, and memory across the lifespan. Thus, the aim of this review was to critically evaluate common theories of age-related cognitive decline and highlight the need for a more comprehensive systems neuroscience approach to cognitive aging.

Age-Related Reductions in Tactile and Motor Inhibitory Function Start Early but Are Independent

Aging is associated with declines in motor and somatosensory function. Some of these motor declines have been linked to age-related reductions in inhibitory function. Here we examined whether tactile surround inhibition also changes with age and whether these changes are associated with those in the motor domain. We tested a group of 56 participants spanning a wide age range (18-76 years old), allowing us to examine when age differences emerge across the lifespan. Participants performed tactile and motor tasks that have previously been linked to inter- and intra-hemispheric inhibition in the somatosensory and motor systems. The results showed that aging is associated with reductions in inhibitory function in both the tactile and motor systems starting around 40 years of age; however, age effects in the two systems were not correlated. The independent effects of age on tactile and motor inhibitory function suggest that distinct mechanisms may underlie age-related reductions in inhibition in the somatosensory and motor systems.

Ageing of the somatosensory system at the periphery: age-related changes in cutaneous mechanoreceptors

Decline of tactile sensation associated with ageing depends on modifications in skin and both central and peripheral nervous systems. At present, age-related changes in the periphery of the somatosensory system, particularly concerning the effects on mechanoreceptors, remain unknown. Here we used immunohistochemistry to analyse the age-dependent changes in Meissner's and Pacinian corpuscles as well as in Merkel cell-neurite complexes. Moreover, variations in the neurotrophic TrkB-BDNF system and the mechanoprotein Piezo2 (involved in maintenance of cutaneous mechanoreceptors and light touch, respectively) were evaluated. The number of Meissner's corpuscles and Merkel cells decreased progressively with ageing. Meissner's corpuscles were smaller, rounded in morphology and located deeper in the dermis, and signs of corpuscular denervation were found in the oldest subjects. Pacinian corpuscles generally showed no relevant age-related alterations. Reduced expression of Piezo2 in the axon of Meissner's corpuscles and in Merkel cells was observed in old subjects, as well was a decline in the BDNF-TrkB neurotrophic system. This study demonstrates that cutaneous Meissner's corpuscles and Merkel cell-neurite complexes (and less evidently Pacinian corpuscles) undergo morphological and size changes during the ageing process, as well as a reduction in terms of density. Furthermore, the mechanoprotein Piezo2 and the neurotrophic TrkB-BDNF system are reduced in aged corpuscles. Taken together, these alterations might explain part of the impairment of the somatosensory system associated with ageing.

Sensory-specific impairment among older people. An investigation using both sensory thresholds and subjective measures across the five senses

Age-related sensory impairment is a slow and gradual progress, which affects multiple modalities. Two contradictory hypotheses exist about the age-related decline of sensory thresholds. The common factor theory assumes one underlying factor-which accounts for the loss of several sensory modalities simultaneously-and the specific factor theory predicts that the sensory decline is uncorrelated between different modalities. In this study, we aimed to explore whether (i) there is a common factor of sensory thresholds in older people, (ii) older people assume that sensory decline in one modality also affects other modalities, (iii) there is a relation between sensory threshold and the subjective assessment of sensory function. This was accomplished by collecting both threshold measures and self-reported ratings for smell, hearing, taste, vision, and touch function in a group of 104 older people (mean age: 67.2 years; SD: 9.85; range: 50-100 years). Results indicated that there was no common factor of sensory thresholds, hence an impairment in one modality did not necessarily imply a shortfall in other modalities. In contrast, our results suggested one or two common factor(s) for the participants' ratings. Participants who reported a diminished function in one sense tended to generalize this rating to the other senses as well. The correspondence between subjective ratings and sensory thresholds was relatively good for vision and audition, although no correlations were observed for the other domains. These findings have implications for clinicians, suggesting that subjective measures should be combined with sensory threshold measurements when evaluating sensory dysfunction. Also, these data convey a positive message for older people and their physicians by showing that loss in one sensory modality does not necessarily generalize to losses across all sensory modalities.