Anticholinergic activity (AA) is generally thought to cause cognitive dysfunction, especially in Alzheimer's disease (AD), one of the neurocognitive disorders related to memory disturbances. Therefore, it is important to evaluate cognitive functions to determine whether they are associated with anticholinergic burden. In Japan, the most frequently used cognitive scale for evaluating cognitive functions is the revised version of Hasegawa's Dementia Rating Scale (HDS-R). However, the relationship between anticholinergic burden and cognitive functions has not been previously examined using the HDS-R. Therefore, here we used the HDS-R to evaluate the relationship between serum anticholinergic activity (SAA) and cognitive functions in 76 patients with AD, 26 of whom had positive SAA [SAA (+)] with a mean of 4.14 ± 2.70 nM. Total scores for orientations to time and place, registration, and recall were significantly lower in the SAA (+) group than in the SAA (-) group (P < 0.05), suggesting potential relationships between SAA and disorientations to time and place in current surroundings as well as memory disturbances. Thus, the disorientations to time and place might explain the clinical features of confusion in current surroundings caused by anticholinergic burden in AD.