The prevalence of dementia in subacute myelo-optico-neuropathy (SMON) patients who underwent medical checkups

Yufuko Saito, Kenichi Sakai, Masaaki Konagaya

Subacute myelo-optico-neuropathy (SMON) is a known adverse effect of clioquinol use; however, clioquinol dissolves beta-amyloid aggregation in Alzheimer's disease (AD). Therefore, we investigated the prevalence of dementia in SMON patients and whether past clioquinol use affected the current incidence of AD. We included 647 SMON patients (195 men, 452 women; mean age 77.9 years) who had undergone medical checkups including the mini-mental state examination (MMSE) in 2012. Of them, 105 patients scored ≤23 on the MMSE assessment. The presence/absence of dementia and disease backgrounds were obtained by a questionnaire. Then, using the medical checkup database, the correlation between the degree of severity when signs of SMON were at their worst and the concurrent presence or absence of AD at present was analyzed. In patients ≥65 years of age, the estimated prevalence of dementia was approximately 10.9% (95% confidence interval: 7.9%-13.8%). The concurrent presence of AD at present was not correlated with the past degree of SMON severity when the SMON signs were at their worst. The 10.9% prevalence of dementia in SMON patients was lower than a previously reported 15% prevalence found in the general population. According to these results, we cannot draw a definitive conclusion regarding the preventive effect of clioquinol on AD. Additionally, the lack of association between the onset of AD and past severity of SMON precludes definitive conclusions on the relationship between concurrent presence of AD and past clioquinol use.