Effects of transcutaneous electrical nerve stimulation on memory and behavior in Alzheimer's disease may be stage-dependent

Background: in previous studies, transcutaneous electrical nerve stimulatio n (TENS) was shown to result in improvements in nonverbal short-term and lo ng-term memory, verbal long-term memory, and verbal fluency in patients in an early stage of Alzheimer's disease (AD). In addition, the patients' phys ical, social, and affective functioning improved. As AD is a progressive di sease, it was examined in the present study whether TENS would still be eff ective in the midstage of AD. Methods: Sixteen subjects (70-91 years old) met the NINCDS-ADRDA criteria f or probable AD, as well as the criteria for stage 6 of the Global Deteriora tion Scale (midstage AD). To evaluate treatment effects, the subjects under went a number of neuropsychological tests and two observation scales. Results: Compared to TENS in an early stage, TENS in the midstage of AD app ears to yield less beneficial effects, i.e., as for cognition only nonverba l short-term memory improved. No treatment effects were observed for the pa tients' physical, social, and affective functioning. Conclusions: In view of the small number of patients, the clinical relevanc e of TENS in patients in a midstage of AD remains to be confirmed in a larg er group, after which more definite conclusions about the stage-dependency of TENS in AD can be drawn. (C) 1999 Society of Biological Psychiatry.