4 | DISCUSSION
To our knowledge, our report is the first to show that lung cancer itself without metastasis can cause cognitive impairment. Cancer of the non-central nervous system has been shown to induce cognitive impairment; however, its mechanism has not been well studied.7 Moreover, little is known of the cognitive function of patients with cancer prior to surgery, with only 3 studies having evaluated the cognitive function of patients newly diagnosed with breast cancer.7
The SAS and pathophysiological evidence in isolation cannot fully explain the patient’s cognitive impairment. SAS can induce cognitive impairment, especially the obstructive form of SAS, which has been associated with general cognitive impairment.8 Our current case presented general cognitive impairment one year after the baseline visit, which gradually worsened despite the successful introduction of CPAP. The patient did not show the typical cognitive impairment of AD, although the pathophysiological findings using PiB-PET, THK5351-PET, and IMP-SPECT indicated AD type impairment.
A limitation of our current report is that, although we observed the patient longitudinally and in detail, we had only one case. Cohort studies investigating non-central nervous system cancers, divided by type, remain to be performed.