2.4 Reason for Absence: ICD Codes

Each absence in the dataset includes a coded reason. Reasons 1 through 21 follow the International Classification of Diseases (ICD), a standardized system used worldwide to categorize medical conditions. Reasons 22 through 28 are additional categories specific to this dataset that capture non-medical absences.

Code	Reason
1	Certain infectious and parasitic diseases
2	Neoplasms
3	Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
4	Endocrine, nutritional, and metabolic diseases
5	Mental and behavioural disorders
6	Diseases of the nervous system
7	Diseases of the eye and adnexa
8	Diseases of the ear and mastoid process
9	Diseases of the circulatory system
10	Diseases of the respiratory system
11	Diseases of the digestive system
12	Diseases of the skin and subcutaneous tissue
13	Diseases of the musculoskeletal system and connective tissue
14	Diseases of the genitourinary system
15	Pregnancy, childbirth, and the puerperium
16	Certain conditions originating in the perinatal period
17	Congenital malformations, deformations, and chromosomal abnormalities
18	Symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified
19	Injury, poisoning, and certain other consequences of external causes
20	External causes of morbidity and mortality
21	Factors influencing health status and contact with health services
22	Patient follow-up
23	Medical consultation
24	Blood donation
25	Laboratory examination
26	Unjustified absence
27	Physiotherapy
28	Dental consultation

Notice that the reasons range from serious medical conditions (codes 1–21) to routine appointments and even unjustified absences (codes 22–28, shown in italics). This variation is itself analytically interesting — later in the book, we will explore whether the type of reason is associated with longer or shorter absences and whether certain reasons cluster among particular employees.