From the Guidelines
The expected rate of decline in FEV1 for healthy nonsmokers is approximately 29 mL per year. This natural decline is part of normal aging as lung elasticity decreases and respiratory muscle strength diminishes over time. The rate of decline can vary based on several factors including sex, height, and environmental exposures. Certain populations may experience different rates - for instance, some studies suggest that women may have a slightly lower rate of decline at approximately 20-25 mL per year. This natural decline becomes clinically significant when comparing to smokers, who typically experience an accelerated decline of 40-60 mL per year. Understanding this baseline rate is important for clinicians when assessing respiratory health over time and distinguishing between normal aging and pathological processes affecting lung function, as noted in a systematic review of the literature 1.
Some key points to consider:
- The rate of decline in FEV1 can be affected by occupational exposures and cigarette smoking 1.
- A study of 211 never-smokers with AAT deficiency found a mean annual decline in FEV1 of 47 ml/year, with a greater decline after age 59 years 1.
- The American Thoracic Society recommends using specific reference equations, such as those from NHANES III, to estimate the rate of decline in FEV1 1.
- The rate of decline in FEV1 can be estimated from the current FEV1, and the most important predictor of future decline is the current rate of decline 1.
Overall, the expected rate of decline in FEV1 for healthy nonsmokers is approximately 29 mL per year, and this rate can be influenced by various factors, including sex, height, and environmental exposures.
From the Research
Expected Rate of Decline in FEV1 per Year in Nonsmokers
- The expected rate of decline in FEV1 per year in nonsmokers is approximately 10.8 mL/yr less than that of continuing smokers, as reported in a study published in 2010 2.
- A study from 2014 analyzing data from the English Longitudinal Study of Ageing found a mean rate of decline in FEV1 of 32.92 ± 0.96 ml/year in older people, with a lower FEV1 level observed in current smokers compared to nonsmokers 3.
- Another study from 2010 estimated that never smokers had a beta (rate of FEV1 decline) of 10.8 mL/yr (95% confidence interval, 8.9 to 12.8) less than continuing smokers 2.
- The rate of decline in FEV1 can vary depending on several factors, including age, sex, smoking status, and baseline lung function, as noted in a 2013 review of longitudinal observational studies and intervention trials in COPD populations 4.
Factors Influencing FEV1 Decline
- Smoking status is a significant factor, with continuing smokers having a higher rate of decline in FEV1 compared to never smokers or ex-smokers 2.
- Age and severity of airflow limitation can also impact the rate of decline in FEV1, with older individuals and those with more severe airflow limitation experiencing a faster decline 5, 3.
- Other factors, such as sex, height, body mass index, and history of sputum production, can also influence FEV1 decline 3.