Changes in the sweatspot test with ageing and relation to cardiovascular autonomic function.

The sweatspot test assesses the local sweat response to an intradermal injection of acetylcholine. It has been reported as a more sensitive indicator of autonomic dysfunction in important diabetic men than either pupillary or cardiovascular tests, and has been used to establish the presence of autonomic dysfunction in patients with idiopathic chronic constipation. However, the usefulness of this test as a simple and quick method of diagnosing autonomic dysfunction in an elderly population has not been established. This is important given the high prevalence of reduced autonomic function with ageing and hypertension. We compared the age-associated responses in the sweatspot test and its relation to cardiovascular autonomic function in elderly normotensive and hypertensive subjects. We studied eleven normotensive and 24 untreated hypertensive elderly subjects (mean age 75.7 years, range 63-85) and compared the results of the sweatspot test to a young control group (n = 11, mean age 32.0 years, range 25-41), and to a standard battery of cardiovascular autonomic function tests. The median sweatspot score was significantly lower in the elderly compared with young subjects (1.9 vs. 12.0, p < 0.0001) although there was no difference between elderly normotensive and hypertensive subjects (1.6 vs. 2.4, p = 0.8). No correlation was demonstrated between the median sweatspot score and the number of abnormal cardiovascular tests. The sweatspot test was grossly abnormal in all elderly subjects and was not correlated to changes in cardiovascular autonomic function. Its diagnostic use in the elderly is therefore of very limited value.