Objective To explore the effect of occupational sleep deprivation on cognitive function of retired nurses and its possible mechanism. Methods One hundred and seven nurses were selected by cluster sampling and their degree of sleep deprivation was assessed by years of night-shift work and frequency of night shift each month. Then they were divided into a sleep deprivation group (n=82) and non-sleep deprivation group (n=25). Cognitive function was assessed by the Mini-Mental Status Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Clock Drawing Test (CDT), and the serum melatonin, low-density lipoprotein and triglyceride were detected to explore the possible mechanism of sleep deprivation on cognitive function. Results Compared with the non-sleep deprivation group, the scores of MMSE and MoCA in the sleep deprivation group were significantly lower, while the levels of total cholesterol, low-density lipoprotein and melatonin were significantly higher (P＜0.05 for all). There were significant differences in orientation, attention and calculation between the sleep deprivation group and non-sleep dep-rivation group (P＜0.05 for both). Sleep deprivation and concentration of low-density lipoprotein were risk factors of cognitive impairment (P＜0.01 for both). Conclusion Occupational sleep deprivation in nurses at young and middle-age has a certain impact on cognitive function during their elderly stage. Low density lipoprotein might be a risk factor of cognitive impairment. Early scree-ning and intervention should be carried out to reduce the risk of developing Alzheimer′s disease among nurses who have engaged in night shift work for a long time.