This study is a single-center, randomized, double-blind, placebo-controlled clinical trial investigating a pharmacological intervention for aging. Its primary objective is to evaluate the efficacy of NMN while ensuring the safety of oral administration, with the aim of identifying effective strategies to delay aging and improve the quality of life in the elderly population. The main outcomes of this study are to characterize the patterns of NMN efficacy across different populations and to identify sensitive biomarkers that reflect responsiveness to the intervention.

Inclusion criteria：

1. Local residents of Quzhou or living in Quzhou for over ten years.
2. age 40-50 and 60-70 years old, no major bad habits.
3. Gender unlimited.
4. in good health and has not undergone major surgery within half a year.
5. Be able to communicate well with researchers and cooperate with the work during the study.
6. Written informed consent can be signed voluntarily.

Exclusion criteria：

1. Alcoholism, heavy smoking (more than 5 packs/day, 20 cigarettes per pack), drug abuse or substance abuse.

2. Participants are conducting other clinical trials or using any research drugs or equipment for treatment within 30 days before enrollment (including but not limited to aspirin, metformin, resveratrol, vitamin C, etc.).

3. Obesity (bmi more than 30).

4. Pregnant/lactating women.

5. Disease history:

   A) under 60 years old:

   1. any cancer (erythrocytosis, except basal cell or squamous cell skin cancer).
   2. coronary artery disease/myocardial infarction/clinically significant congestive heart failure.
   3. stroke/transient ischemic attack.
   4. deep vein thrombosis/pulmonary embolism.
   5. serum creatinine > 1.5 mg/dl (male).
   6. poor control of hypertension (although treated, there is still significant hypertension (systolic blood pressure > 160 mmHg, or diastolic blood pressure >100 mmHg)).
   7. history of active liver disease or metabolic acidosis.
   8. chronic kidney disease/hemodialysis treatment, history of severe kidney damage and/or EGFR ≤ 45ml/min/1.73m2.
   9. severe autoimmunity/inflammation, such as rheumatoid arthritis, lupus, Crohn's disease, etc.
   10. nervous system diseases such as dementia, such as Alzheimer/Parkinson's disease.
   11. diabetes mellitus (hemoglobin > 6.5% or fasting blood glucose > 126 mg/dL or taking diabetes drugs or insulin treatment).
   12. recent (within 3 months) cardiovascular events (myocardial infarction, coronary intervention, coronary artery bypass grafting).
   13. infectious diseases such as HIV, hepatitis, tuberculosis, etc.
   14. hand or lower limb disability affects normal function and life.

   B) older than 60 years:

   1. any cancer (erythrocytosis, except basal cell or squamous cell skin cancer).
   2. history of active liver disease or metabolic acidosis.
   3. chronic kidney disease/hemodialysis treatment, history of severe kidney damage and/or EGFR ≤ 45ml/min/1.73m2.
   4. severe autoimmunity/inflammation, such as lupus, Crohn's disease, etc.
   5. nervous system diseases such as dementia, such as Alzheimer/Parkinson's disease.
   6. recent (within 3 months) cardiovascular events (myocardial infarction, coronary intervention, coronary artery bypass grafting).
   7. infectious diseases such as HIV, hepatitis, tuberculosis, etc.
   8. hand or lower limb disability affects normal function and life.

6. Currently taking the following drugs regularly:

   A) chemotherapy drugs (such as tamoxifen, adriamycin, mitoxantrone, bleomycin). B) antiplatelet drugs (e.g., clopidogrel/Plavix, dipyridamole/anglionide, ticlopidine/ticlopidine, except aspirin).

   C) cholinesterase inhibitors for Alzheimer's disease (donepezil/alicept).

7. The researchers believe that the physical factors of the participants may have an adverse impact on the research process or results.