Mild cognitive impairment1 is an intermediate stage between the normal cognitive decline expected in old age and the early stages of dementia such as Alzheimer's, which can cause problems related to memory, language, thinking, and judgment. If a person suffers from a mild cognitive disorder, his/her memory and mental functions may be weakened.1 Further, with the progress of the disease, the person gradually loses his sense of independence, fails to achieve goals and has serious problems in social interactions, these issues cause depression, anxiety, aggression, decrease in self-confidence, lack of satisfaction and feeling of inadequacy in the person.2 Cognitive impairment (especially functional impairment) is one of the main symptoms of vascular dementia, which can cause impairments in mood and behavior and decrease the quality of life. Although the relationship between mild cognitive impairment and cerebrovascular disease has not been fully clarified, vascular dementia, which is the most common dementia after Alzheimer's disease,2 can be prevented by controlling vascular risk factors, including high blood pressure and diabetes.3,4 Dementia refers to a disease process characterized by progressive cognitive decline that remains intact in the field of consciousness. As the population ages, the prevalence of dementia is increasing and it is about 5 % in the population over 65 years old, 20 to 40 % in people over 85 years old, 15 to 20 % in outpatients and 50 % in chronic disease care centers.5

Another important side effect of brain vascular disorders is the change in sleep pattern of patients. This complication can be due to a disorder in removing waste materials from the cerebrospinal fluid and brain cells. In this regard, we mention the relationship between sleep and dementia in different studies.6 Sleep is very important for central nervous system3 physiology. Changes in the quality of sleep and its structure occur throughout life and become prominent during healthy aging. Several studies have shown a link between sleep and CNS disorders, such as cerebrovascular disease, Parkinson's disease, multiple sclerosis, epilepsy, headache, pain, and especially neurodegenerative disorders. Alzheimer's disease is the most common neurodegenerative disorder and is associated with sleep problems.7

So far, no definitive drug or specific surgical method has been identified for the prevention and treatment of vascular dementia, and only protective symptomatic treatments are used to relieve accompanying psychiatric symptoms in patients.8 Since cognitive disorders, especially vascular dementia, may present with several symptoms, symptomatic treatment requires a multimodal pharmacological strategy. Many people with vascular dementia or other types of dementia and their caregivers use complementary medicines. Common complementary medicine interventions for vascular dementia include herbal medicine, acupuncture, nutritional supplements, yoga, tai chi, and music therapy.3 Also, the findings have shown that the extracts of plants such as devil's thorn or white thorn and olive leaves have neuroprotective effects. Herbal medicines are used to treat and prevent psychiatric symptoms as well as modifiable risk factors such as high blood pressure and diabetes, which can be significantly effective in the prognosis of patients with vascular dementia.1 Among all these plants mentioned above, Bacopa monnieri and its active ingredient have been exclusively active in the field of nerve regeneration. It has been proven that Brahmi (another name of bacopa) has antioxidant activity and protection against neurons, so it is considered the most promising plant in the treatment of Alzheimer's.9 Recently, new saponins named bacopazides I-XII have been identified to clarify the anti-dementia effects of this plant.10 In a 2016 study by Kumar et al., a six-week randomized, placebo-control trial aimed at the effect of Bacopa monnieri extract on cognitive functions of medical students. The results of this study showed that different neuropsychological tests showed a statistically significant improvement in the Bacopa group compared to the control treated group.11

Therefore, according to middle-aged and elderly people suffering from vascular risk factors such as high blood pressure, high blood fat, diabetes and obesity, a large number of studies showed that when all four risk factors are present in middle-aged and old age, there is a risk of cognitive disorders. Therefore, due to the popularity of complementary medicine and especially herbal medicines, as well as the lack of sufficient studies on Bacopa monnieri plant and the properties of this plant on the risk factors of vascular dementia, and it can significantly reduce MCI disease, which is considered the stage before Alzheimer's disease. therefore, a research was conducted with the aim of "Effect of Bacopa monnieri extract on cognitive function and sleep quality of patients with mild cognitive impairment".