This study evaluated the diurnal and inter-subject variability of cerebrospinal fluid biomarkers related to Parkinson's disease and Alzheimer's disease. Cerebrospinal fluid samples were collected from healthy volunteers and Parkinson's patients at multiple time points over 26 hours and two weeks apart. The results showed that alpha-synuclein, Abeta 1-42, and Abeta 1-40 levels increased over the sampling period, while DJ-1 levels remained constant. Between subjects, alpha-synuclein was higher in males, and DJ-1 was associated with age. For both healthy and Parkinson's groups, the biomarkers demonstrated intra-subject consistency over two weeks.