Cohort profile: The Obesity and Disease Development Sweden (ODDS) study, a pooled cohort.

Purpose: The Obesity and Disease Development Sweden (ODDS) study was designed to create a large cohort to study body mass index (BMI), waist circumference (WC) and changes in weight and WC, in relation to morbidity and mortality.

Participants: ODDS includes 4 295 859 individuals, 2 165 048 men and 2 130 811 women, in Swedish cohorts and national registers with information on weight assessed once (2 555 098 individuals) or more (1 740 761 individuals), in total constituting 7 733 901 weight assessments at the age of 17-103 years in 1963-2020 (recalled weight as of 1911). Information on WC is available in 152 089 men and 212 658 women, out of whom 108 795 have repeated information on WC (in total 512 273 assessments). Information on morbidity and mortality was retrieved from national registers, with follow-up until the end of 2019-2021, varying between the registers.

Findings To Date: Among all weight assessments (of which 85% are objectively measured), the median year, age and BMI (IQR) is 1985 (1977-1994) in men and 2001 (1991-2010) in women, age 19 (18-40) years in men and 30 (26-36) years in women and BMI 22.9 (20.9-25.4) kg/m in men and 23.2 (21.2-26.1) kg/m in women. Normal weight (BMI 18.5-24.9 kg/m) is present in 67% of assessments in men and 64% in women and obesity (BMI≥30 kg/m) in 5% of assessments in men and 10% in women. The median (IQR) follow-up time from the first objectively measured or self-reported current weight assessment until emigration, death or end of follow-up is 31.4 (21.8-40.8) years in men and 19.6 (9.3-29.0) years in women. During follow-up, 283 244 men and 123 457 women died.

Future Plans: The large sample size and long follow-up of the ODDS Study will provide robust results on anthropometric measures in relation to risk of common diseases and causes of deaths, and novel findings in subgroups and rarer outcomes.