FGF21 and chronic obstructive pulmonary disease: With the same model, high GDF15 (HR 1.386, 95% CI 0.869–2.209, p = 0.171) and FGF21 (HR 0.986, 95% CI 0.640–1.518, p = 0.948) were not independent risk factors for moderate COPD exacerbation (data not shown).