Skin heat dissipation: the influence of diabetes, skin thickness, and subcutaneous fat thickness.
BACKGROUND
It is well established that diabetes impairs vascular endothelial function. However, the impact of impaired endothelial function on thermal conductivity of the skin, especially in relation to a constant versus a sudden heat stress, has not been established. Further, there is some evidence that aging reduces skin dermal thickness and subcutaneous fat thickness. Since these are important determinates of heat dissipation by the skin, these parameters also need to be examined in people with diabetes.


METHODS
Ninety subjects (30 younger individuals, 30 patients with diabetes, and 30 patients age-matched to the diabetes subjects) participated in two series of experiments to determine (1) the thickness of the subcutaneous fat layer and skin thickness and the skin response to a sudden heat stress and (2) the response to a continuous heat stress on the lower back. Skin thickness and subcutaneous fat thickness were assessed by ultrasound, and skin blood flow was examined by infrared laser Doppler flow meter.


RESULTS
People with diabetes had significantly less resting blood flow, blood flow in response to a single or continuous heat load, less subcutaneous fat, and thinner skin than either age-matched controls or younger people (P < 0.05). Subjects with diabetes also had the lowest concentration of red blood cells in their skin, implying a reduction in the number of capillaries in the skin.


CONCLUSIONS
Thinning of the skin and probably a reduction in capillaries in the dermal layer contribute to a reduction in the blood flow response to heat. People with diabetes, in particular, have reduced skin heat dissipation because of less resting blood flow and thinner skin than that seen in age-matched controls.
Petrofsky
Jerrold S
JS
Department of Physical Therapy, School of Allied Health Professions, Loma Linda University, Loma Linda, CA 92350, USA. jpetrofsky@llu.edu
McLellan
Katie
K
Bains
Gurinder S
GS
Prowse
Michelle
M
Ethiraju
Gomathi
G
Lee
Scott
S
Gunda
Shashi
S
Lohman
Everett
E
Schwab
Ernie
E
D000273:Adipose Tissue / Q000473:pathology / Q000503:physiopathology*; D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D015992:Body Mass Index; D001831:Body Temperature; D003920:Diabetes Mellitus / Q000503:physiopathology*; D006358:Hot Temperature; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008833:Microcirculation / Q000502:physiology*; D008875:Middle Aged; D012867:Skin / Q000098:blood supply / Q000503:physiopathology*; D015595:Skin Aging; D012879:Skin Physiological Phenomena; D012881:Skin Temperature / Q000502:physiology*; D012885:Skinfold Thickness; D055815:Young Adult