The preclinical stage of Alzheimer's disease (AD) has become a major focus of research attempting to develop effective treatments for AD. In preclinical AD, specifically at its early stage although magnetic resonance imaging (MRI), brain perfusion single photon emission tomography (SPECT), or neuropsychological tests are unlikely to detect sings of the disease, positron emission tomography (PET) imaging is capable of visualizing the abnormal accumulation of beta amyloid (Aβ), which is known as being Aβ positive. Research shows that amyloid deposition begins approximately 15 to 20 years before the onset of AD. Although clinical trials conducted all over the world require the disclosure of amyloid PET scan results to cognitively normal participants, ethical questions have been raised over whether the amyloid status should be disclosed to the population, given that there is no complete cure available for AD. In other words, appropriate standards for disclosure should be established, as the scan results in both research and clinical settings are seen to be disclosed to an increasing number of cognitively normal persons with or without elevated Aβ. Historically, excessive emphasis on the principle of "non-maleficence" has led to a "no-return policy" in clinical trials, but another principle of "respect of autonomy" has increasingly been revalued to play a fundamental role even in disclosure practices under such circumstances. Among cognitively healthy persons, additional attention needs to be paid to those who complain subjective cognitive decline (SCD). Research suggests not only that SCD may be the first symptomatic manifestation of AD, but also that persons with SCD tend to have more anxiety and depressive symptoms. We conducted amyloid PET scans on participants who visited a memory clinic reporting subjective cognitive decline but showing no objective abnormalities in cognitive function. All participants preferred to know the scan results. No change was observed over time until 24 weeks after disclosure in anxiety, depression, or test-related distress. Therefore, disclosing amyloid status to cognitively healthy persons with subjective cognitive decline did not result in a significant violation of the non-maleficence principle. Regarding the benefits of disclosing the PET results, on the other hand, studies have reported that participants were able to make plans and decisions for their life in advance. It is true that amyloid imaging has a limitation in predicting the development of AD in the future; but, more importantly, efforts must be made to ensure best practices in providing risk communication including such uncertainty to cognitively healthy participants, as well as persons in other stages of AD.
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