1) Adult asthma cohort):BMI was significantly and monotonously associated with reduced circulating CC16 levels in adult asthmas patients. Also, CC16 was inversely associated with sputum eosinophils and blood periostin. Patients with the lowest tertile of serum CC16 levels at baseline had a -14.3 mL decline in FEV1 than those with the highest tertile over five years of follow-up (p for trend = 0.031).
2) Population 2 (birth cohort): Ongoing.
3) Animal study: The percentage of CC16-cells was reduced in the small airways of mice with obesity. In addition, serum CC16 levels were significantly lower in obese mice than in non-obese control mice. However, the serum levels of SP-A and SP-D, other products of club cells, did not vary between obese and non-obese control mice.