A global obesity epidemic has occurred among both adults and children during the last three decades . Among patients with chronic obstructive pulmonary disease (COPD), low body mass index (BMI) is associated with poor prognosis and excess mortality , while obesity appears protective , a phenomenon known as the obesity paradox. Still, in milder forms of COPD, obesity is associated with increased risk of mortality, possibly mediated via the strong association with diabetes and hypertension . Furthermore, abdominal fat accumulation is the strongest predictor of lung function impairment , and abdominal circumference is almost twice as high in COPD patients as in sex- and age-matched controls . Thus, previous studies on the relationship between BMI and COPD have evaluated the associations for adult BMI, while it is unknown if BMI during childhood or adolescence, i.e. many years before onset of COPD, predicts the development of
COPD later in life.