2.2. Conscription data

Another way of analyzing nationally representative anthropometric data is to use the health data of recruitment for the Swiss Armed Forces, which has been carried out in a standardized manner throughout the year since 1875. In the present study, we reuse data published previously in 2019 as well as from historical years (1990s, 1950s, 1930s, 1870s). These conscription data usually cover around 90–95% of all male Swiss citizens in early adulthood. The estimated 5–10% of male birth cohorts who do not show up for screening at conscription represent the full spectrum of severe physical and mental diseases and impairment, which are not necessarily associated with overweight and height (Panczak et al., ²⁰¹⁴). Therefore, the coverage of the Swiss conscription data is considered very high and sample selection bias is not regarded as an issue.

The data from 2019 consist of 25 724 male conscripts between 18 and 21 years. In addition to the measurement of body height and weight, the Swiss Armed Forces have added waist circumference measurements as a new standard as of the beginning of 2019.

The occupation of the conscript is the only variable that gives an indication of the socio‐economic background at the individual level. According to previous studies, the occupations of the conscripts were assigned to the Socio‐Economic Index of Occupational Status (ISEI‐08). The ISEI allows the comparison of occupations according to their socio‐economic status. It can take on values between 16 (agricultural assistants) and 90 (judges) and was also used, for example, for the PISA studies as an indicator of socio‐economic status associated with occupation. The ISEI‐08 distribution of the occupations of those subject to compulsory military service was divided into three equally large groups (terciles). In addition, pupils, high school graduates and students together form a separate group, as well as those who have no or insufficient information on their occupation. The age of the conscripts was only available in one‐year groups, and the allocation to the major regions was based on the ZIP codes of the place of residence (assignment was done by Armed Forces personnel before data delivery).

The 1990s and 2019 data sets were made available by the Medical Service (Swiss Armed Forces ‐ Armed Forces Staff ‐ Medical Service Division) on a contractual basis in accordance with the legal data protection requirements. The data were exported from the Medical Information System of the Armed Forces (MEDISA) by the Medical Department and completely anonymized in accordance with the specifications before being handed over to the study team. Due to the anonymization of the data based on the Human Research Act (HRA) and before data delivery to the study team, there was no obligation to obtain approval from an ethics committee.