Alzheimer-associated urine neuronal thread protein level increases with age in a healthy Chinese population

Alzheimer-associated neuronal thread protein (AD7c-NTP) has been found to be a biomarker for Alzheimer's disease (AD) with elevated levels in the cerebrospinal fluid and urine from AD patients in the early stage of the disease. Whether the urine level of AD7c-NTP in healthy people is age-related is still unclear. We aimed to measure the level of urine AD7c-NTP in a healthy Chinese population of different ages. Urine samples of 294 subjects were collected from the Department of Health Examination Center at Xuanwu Hospital of Capital Medical University, China. The samples were divided into five groups by age: Group 1 (20-29 years), Group 2 (30-39 years), Group 3 (40-49 years), Group 4 (50-59 years) and Group 5 (⩾ 60 years). The Mini Mental State Examination and Montreal Cognitive Assessment were carried out. The level of AD7c-NTP in the urine specimen was detected by enzyme-linked immunosorbent assay. The urine AD7c-NTP levels in Group 1, 2, 3, 4 and 5 were 0.3012 ± 0.2373, 0.3702 ± 0.2422, 0.3914 ± 0.2442, 0.4844 ± 0.2908 and 0.5880 ± 0.2638 ng/ml (mean ± standard error of the mean), respectively. The urine AD7c-NTP levels among the five groups differed significantly (F=6.181, p=0.00). Females had a higher urine AD7c-NTP content than males, and the urine AD7c-NTP level increased with age (r=0.28, p=0.00). To our knowledge this study is the first to show that urine AD7c-NTP level increases with age in a healthy Chinese population without cognitive dysfunction. This study suggests that different cut-off values aimed at different age groups should be established for diagnosing cognitive impairments in clinical practice.