Inflammation measured by C-reactive protein (CRP) has been recommended for measurement in persons of intermediate global risk assessed by the Framingham Risk Score (FRS). Forced vital capacity (FVC), as a measure of pulmonary function, is associated with CRP and is also a predictor of all-cause mortality; however it is not known if the predictive utility of FVC depends on FRS and CRP. Therefore, we examined whether the prediction of all-cause mortality by FVC depends on CRP and FRS in U.S. adults.
We examined 5,448 (projected to 60.6 million) U.S. adults aged 20–79 in the Third National Health and Nutrition Examination Survey who were never-smokers (defined by self report and cotinine level ≤;25 ng/ml), without obstructive lung disease, and had available FVC and CRP data. We performed Cox proportional hazards regression for hazard ratios (HR) and 95% confidence intervals (CI) to examine whether FVC (categorized as: low ≤;85%, borderline 86–94%, and normal ≥ 95%) and CRP (categorized as: low ≤;3 mg/L vs high > 3 mg/L) within FRS groups (low risk < 10%, intermediate risk 10–20%, high risk ≥ 20% or diabetes or CVD) predict all-cause mortality.
FVC did not predict mortality in low FRS persons regardless of CRP. However, those with low FVC paired with high CRP had a significantly higher risk of all-cause mortality (HR=4.47, CI: 1.91–10.45, p < 0.01 in those with intermediate FRS and HR=3.13, CI: 1.36–7.21, p < 0.01 in those with high FRS) when compared to a normal FVC paired with low CRP. FVC did not predict mortality in these groups when CRP was normal.
Low FVC contributes to increased mortality risk only when CRP is elevated in adults with intermediate or high FRS risk; however, when CRP is normal, FVC does not appear to be effective in risk stratification regardless of FRS.
Evaluation of lung function along with inflammation may be useful to improve risk stratification in these individuals, but in low risk persons, evaluation of lung function may not be helpful.
Hwa Lee, No Financial Disclosure Information; No Product/Research Disclosure Information