Can the association of adult lung function with weight in early life be explained by early life factors

Introduction Weight in early life is known to be associated with forced vital capacity (FVC) in adulthood, but whether it is also associated with airflow obstruction (FEV1/FVC) in adulthood is unclear. The observed association between weight in early life and lung function could be confounded by maternal risk factors, such as maternal smoking. Therefore, we examine whether maternal factors might explain this association. Methods Using linear regression among 3,832 participants of the Northern Finland Birth Cohort 1966, we examined the association of adult lung function (FVC and FEV1/FVC) with weight in early life (birth weight and weight gain in the first year of life). We then tested whether this association could be explained by maternal factors (maternal weight, height, BMI, age, smoking, education, socio-economic status and parity) by adjusting for them. Results FVC was positively associated with birth weight and weight gain. FEV1/FVC was not associated with birth weight and was negatively associated with weight gain. Mean FVC in adulthood (95%CI) increased by 86mL (51,121) and 24mL (7.7, 40) for each kilogram increase in birth weight and weight gain, respectively. One kg increase in weight gain was associated with a reduction of 0.003 units (-0.004,-0.001) of FEV1/FVC. Although several maternal factors were associated with both adult lung function and weight in early life, adjusting for them did not substantially alter the results. Conclusion Adult lung function and weight in early life were both associated with several early life factors, but these did not explain the association between adult lung function and weight in early life.