Smoking is the leading worldwide cause of preventable deaths, primarily involving the respiratory and cardiovascular systems. Airflow and vascular flow are highly correlated in smokers. However, spirometry, an easy way to measure airflow, has been unimpressive in helping smokers quit their addiction, perhaps because reduced airflow is often within statistically normal limits and has not been interpreted as increased physiological lung age. We desired to develop and evaluate a new lung age formula based on %FEV1/FEV6 rather than the current Morris and Thomas lung age formulas based on height and FEV1or FVC.
We used the Third National Health and Nutrition Evaluation Survey (NHANES-3) spirometric data of adult never-smokers and established that in all six ethnic-gender groups, the normally distributed %FEV1/FEV6=96.9–0.189xyears–1.524xFVC(L). Since the reciprocal of 0.189 approximates 5, we calculated changes in lung age years by using 5X(predicted-actual)%FEV1/FEV6 for 5800 NHANES-3 never-smokers and 3500 current-smokers. Since the earlier formulas were derived from Caucasians, we also compared results of their and our formulas in only Caucasian adults.
Using %FEV1/FEV6, mean lung ages of six ethnic-gender adult groups of never-smokers closely approximated actual lung ages while values using the earlier formulas were erratic. Using only the current-smoking Caucasian population, mean increases in lung age, based on %FEV1/FEV6, progressed to over 25 years by ages 50 and above, much higher but less erratic than using lung ages based on height and FEV1 or FVC. In comparing surviving Caucasian current-smokers to never-smokers in the 6th, 7th, and 8th decades, over twice as many men and 1.6 times as many women had increased lung age.
Using the ratio of %FEV1/FEV6 rather than absolute values of height and FEV1 or FVC, all decades of NHANES-3 Caucasian current-smokers have significantly increased lung age.
When current-smokers’ airflow values are low but still within statistically normal limits, it is sensible and more persuasive to tell them their increased physiological lung age rather than that their spirometry is normal.
James Hansen, No Financial Disclosure Information; No Product/Research Disclosure Information