The most prevalent chronic disease among senior people, and its prevalence rises with age, is Alzheimer’s disease (AD). One study predicts that the prevalence of dementia will triple globally by 2050. Sleep disorder (sleep disturbance) is a condition that also often occurs in the elderly population. More than about 25%~60% of AD patients have sleep disturbances or circadian rhythm changes. But the sleep disorders during the early stage of AD have not been uniformly recognized. Of the stages of AD, those experiencing the early stage have the most patients. Therefore, this paper summarises the conditions and types of sleep disorders in the first stage of AD, and the articles of sleep disorders of that time lesions are retrieved and analysed. This paper also deals with two pathological mechanisms during early AD: beta amyloid (Aβ) accumulation and tau protein entanglement. By describing the effects of two western drugs and a Chinese herbal medicine, this paper shows that sleep disorders in older adults may suggest mild cognitive impairment and that more attention needs to be paid to what current research suggests. Early AD lesions can lead to sleep disorders and the search for more accurate biomarkers will be a major driver in the development of diagnostics that may delay AD onset.