Ageing reduces skin wetness sensitivity across the body.

Abstract

What is the central question of this study? Ageing impairs the skin's thermal and tactile sensitivity: does ageing also induce loss of skin wetness sensitivity? What is the main finding and its importance? Older adults show an average 15% loss of skin wetness sensitivity, with this sensory deficit being mediated by a combination of reductions in skin's tactile sensing and hydration status. These findings increase knowledge of wetness sensing mechanisms across the lifespan. Humans use sensory integration mechanisms to sense skin wetness based on thermal and mechanical cues. Ageing impairs the skin's thermal and tactile sensitivity, yet we lack evidence on whether wetness sensing also changes with ageing. We mapped local skin wetness and temperature sensitivity in response to cold-, neutral- and warm-wet stimuli applied to the forehead, neck, lower back, dorsal foot, index finger and thumb, in 10 Younger (22.4±1.1years) and 10 Older (58.2±5.1years) males. We measured local skin temperature and conductance (i.e., a marker of hydration status) at the tested sites, to establish the role of skin's thermal and mechanical parameters in ageing-induced changes in wetness sensing. Irrespective of body site, Older reported overall lower wetness perceptions than Younger across all wet-stimulus temperatures (mean difference: -14.6mm; 95% CI: -4.3, -24.9; P=0.008; ∼15% difference). When considering regional wetness sensitivity, the effect of ageing was more pronounced in response to the cold-wet stimulus over the lover back (mean difference Older vs. Younger: -36.8mm; 95% CI: -68.4, -5.2; P=0.014; ∼37% difference) and dorsal foot (mean difference: -37.1mm; 95% CI: -68.7, -5.5; P=0.013; ∼37% difference). We found no differences between age groups on overall thermal sensations (P=0.744) nor local skin temperature (P=0.372); however, we found that Older presented overall lower skin conductance than Younger (mean difference: -1.56μS; 95% CI: -0.49, -2.62; P=0.005), which corresponded to an ∼78% reduction in skin hydration. We conclude that skin wetness sensing decreases with ageing primarily due to age-induced changes in skin mechanics and tactile sensitivity.