Examining adverse effects in a large clinical trial of rTMS application as a treatment for Alzheimer's disease.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) has several advantages compared to other interventions for neurological and psychological disorders. However, various adverse effects have been reported in rTMS research, and little is known about who is most susceptible to rTMS adverse effects, or how they can be minimized. AIMS: We aimed to identify risk factors for adverse effects reported in a recent clinical trial examining rTMS as a treatment for Alzheimer's disease (AD). We hypothesized that higher stimulation intensity would be associated with experiencing unspecified pain/discomfort, dental pain, headache, jaw pain, and muscle contractions, but not be associated with other adverse effects. METHODS: Using detailed notes from treatment sessions, 10 adverse effects were identified. Spearman correlations were conducted to assess relationships between the highest applied stimulation intensity and normalized frequency of each adverse effect amongst those who experienced that adverse effect. Demographic information, cognitive scores, and withdrawal status were compared between the binarized groups of participants who experienced adverse effects versus those who did not. Spearman correlations were also conducted on the binarized adverse effects and the highest applied stimulation intensity. Logistic regressions were conducted to identify potential risk factors. RESULTS: In both the sham and active treatment groups, unspecified pain/discomfort was the most common adverse effect, followed by muscle contractions and dizziness. In both the active and sham treatment groups, stimulation intensity was positively associated with muscle contractions, but was not significantly related to any other adverse effect. In evaluating groups with/without adverse effects, we found there was a significantly higher proportion of males reporting adverse effects in both the active treatment group and the sham treatment group compared to females. CONCLUSION: The findings of this study are a step toward understanding how researchers can minimize such adverse effects, and thereby, create a less aversive experience for rTMS participants.