The purpose of this study is to form a chronological map of common diseases and rare diseases in Chinese population by determining the prevalence of different diseases in each age group.

Studying the distribution of various diseases in specific populations can help explore the causes of diseases, elucidate the distribution patterns, and develop preventive and control measures. Based on an overall assessment of prevalence, the combination of relevant results with age at diagnosis for multiple diseases is important for further understanding of the distribution of diseases at the population level. Therefore, this study aims to form a chronological map of common diseases and rare diseases in Chinese population by determining the prevalence of different diseases in each age group, thus providing a reference for more effective prevention, diagnosis and treatment of diseases.

Inclusion Criteria:

1. All inpatients within the period of January 1, 2017 to December 31, 2021.
2. Patients with discharge diagnosis.
3. Patients with accurate gender and age records.

Exclusion Criteria:

1. Morbidity and mortality due to external causes, i.e. injuries, poisonings and other adverse events due to external environment and accidents.
2. Pregnancy-related conditions.
3. Symptoms, signs, abnormal clinical and laboratory findings.
4. Traditional Chinese Medicine diagnosis records.
5. Patients with incorrect or missing disease codes.

All inpatients within the period of January 1, 2017 to December 31, 2021.