Study population
This was a cross-sectional study performed at the Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University, Shanghai, China. The participants were randomly selected from two communities in districts with long-term stable populations (Pandongli and Jingfenglu), because the age and sex distribution data were similar to those of the 2007 Shanghai census. In brief, the study population consisted of participants aged between 35 and 75 years (n=4813) who underwent head MRI between June 2007 and June 2011. Exclusion criteria included participants who refused to take part in the study or were not adherent, as well as those who were not suitable for MRI, such as cases involving a pacemaker or metallic implant, the early stage of pregnancy, dentures, or claustrophobia. The study protocol was reviewed and approved by the ethics committee of the Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University. All participants provided informed consent prior to study enrollment 19.