This is a 48-week, double-blind, randomized, placebo-controlled study. Sixty-four patients are randomly assigned to take NBP (600mg per day) or placebo for 48 weeks, with 32 patients in each treatment group. Anti-dementia treatment-naive patients meet the inclusion/exclusion criteria are enrolled.

Patients are assigned to NBP will take 200mg tid daily. Patients are visited at baseline, as well as 4, 12, 24, 36, 48weeks after baseline. Safety data is recorded until an additional 30 days after the last treatment (48 weeks).

The primary outcomes include cognitive function and activities of daily living (ADL). All subjects are assessed at baseline, 4w, 12w,24w, 36w intermittent visit and 48w endpoint with the Auditory Verbal Learning Test (AVLT), the Brief Visuospatial Memory Test-Revised (BVMT-R), the Symbol Digit Modalities Test (SDMT), the Trail Making Test-A/B (TMT-A/B), the Benton Judgment of Line Orientation (JLO), the verbal fluency test, the Boston Naming Test (BNT), the Controlled Oral Word Association Test (COWAT), the Stroop test, the Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) and the ADL. The secondary outcomes include the global function and behavioral and psychological symptoms of dementia (BPSD), which are evaluated with the Clinical Dementia Rating (CDR) and the Neuropsychiatric Inventory (NPI), respectively. Independent raters who are blinded to patients' distribution are assigned to assess the participants.

The exploratory outcomes are markers of vascular regulation, including circulating endothelial progenitor cells (EPCs), white matter hyperintensities (WMH) on MRI, cerebral blood flow (CBF) measured with transcranial Doppler (TCD) and arterial spin labeling (ASL) MRI, and parameters of carotid duplex ultrasonic (CDU). In addition, apolipoprotein E (APOE) polymorphism and plasma biomarkers are also detected.

Safety are assessed at each visit.

Inclusion Criteria:

1. Patients meet the criteria of major neurocognitive disorder in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5);
2. Patients aged with 50-80 years, years of education no less than 3, an MMSE range of 15~26, an MoCA < 26, an Hamilton Depression Scale (HAMD) < 17;
3. The MRI (one research dedicated machine 3.0 T) features satisfy subcortical small vessel disease, including (1) multiple (>=3) supratentorial subcortical lacunes (3-20 mm in diameter), with/without white matter hyperintensities (WMH) of any degree; (2) moderate to severe WMH (score>= 2 according to the Fazekas rating scale in either periventricular region or deep white matter) with/without lacunes; (3) one or more strategically located subcortical small infarcts in the deep grey matters;
4. Patients or legal representative should sign the informed consent and have a reliable caregiver.

Exclusion Criteria:

1. Cognitive impairment caused by other central nervous system diseases, such as AD, dementia with Lewy body, frontal-temporal lobe degeneration, etc;
2. Cognitive impairment due to other conditions, such as severe depression, vitamin B 12 deficiency, abnormal thyroid function, etc;
3. Alcoholism, drug abuse or other conditions influenced the evaluation of cognition;
4. Patients unable to undertake MRI assessment.
5. Patients with a history of other severe disease such as epilepsy, myocardial infarction or heart failure will be excluded;
6. Administration of other investigational drugs, psychotropic drugs, drugs with psychiatric side effects, and oral anticoagulants are not allowed

De-identified individual participant data for all primary and secondary outcome measures will be available

Data will be available within 6 months of study completion.

Data access requests will be reviewed by an external Independent Review Panel. Requestors will be required to sign a Data Access Agreement.