Age-related circadian rhythm and variability of large- and small-airway function in healthy non-smoking adults: Data from 7-day diurnal and nocturnal home monitoring using an electronic portable spirometer

Abstract

Background: The aim of the study was to investigate the possible influencing factors of the large- and small-airway function variation in healthy non-smoking adults.

Methods: Healthy non-medical non-smoking adults were enrolled in this prospective cohort study. Each participant took the portable spirometer test relying only on video teaching. Then conventional spirometry and bronchodilation test were conducted using a Jaeger spirometer, followed by 7-day diurnal and nocturnal home monitoring using a portable spirometer.

Results: A drop in both large- and small-airway function began at about 25 years of age, and a rapidly decline at about 50 years. The CV of FEV₁ (r = 0.47, P = 0.0082) and small-airway function variables correlated with age (r ≥ 0.37, P < 0.05 for both MEFs and MEFs/FVC), especially for evening small-airway function variables. The CV of large (4.666 ± 1.946, P = 0.002 for FEV₁; 4.565 ± 2.478, P = 0.017 for FEV₃) and small airways (10.38 ± 3.196, P = 0.031 for MEF50 and 11.21 ± 4.178, P = 0.023 for MMEF) was higher in the 45- to 60-year subgroup than in the 30- to 45-year and 18- to 30-year subgroups.

Interpretation: Age was the main influencing factor of both central and peripheral airway function variability, especially for the small-airway function in the evening. The LLN of small-airway variables varies depending on the age and circadian rhythm. People older than 45 years should pay more attention to monitoring small-airway function in the evening, which will be helpful for early clinical detection of those at high risk for asthma.

Trial registration number: ChiCTR2100050355.

Keywords: age; circadian rhythm; home monitoring; small airway function; variation.

Figure 1

Schematic presentation of study design. A total of 36 adults were invited to participate, among which one participant quit the study after conducted the first GOSPT2000 test and 35 adults attended and completed the 7-day portable spirometer and laboratory pulmonary function tests; of these, three participants were excluded from the data analysis as their FEV₁/FVC was < 70% on the first GOSPT2000 test, and one person was excluded from final analysis as data did not meet the quality control criteria, leaving 31 participants for the final data analysis in the present study. After the first portable GOSPT2000 test, the subjects were asked to complete the spirometry and bronchodilation test using a Jaeger spirometer under the guidance of a trained medical technician on the same morning. The quiescent period between measurements was 20 mins after completing the spirometry and bronchodilation test. Then, the subjects took the GOSPT2000 device home and completed the pulmonary function monitoring in the home setting for the next 7 consecutive days. FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; MEF50: forced expiratory flow at 50% of forced vital capacity; MEF25, forced expiratory flow at 75% of forced vital capacity; MMEF, forced expiratory flow between 25 and 75%; PEF, peak expiratory flow; SD, standard deviation; CI, confidence interval; t-, total; m-, morning; e-, evening.

Figure 2

Correlation of pulmonary function (total, morning, and evening) with age, height, weight, and BMI (N = 31, except N = 30 for PEF). Both large- and small-airway function variable values were strongly negatively related to age, and were dramatically positively related to height (A). Similar correlation both in the morning and the evening was found (B). FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; MEF50: forced expiratory flow at 50% of forced vital capacity; MEF25: forced expiratory flow at 75% of forced vital capacity; MMEF: forced expiratory flow between 25 and 75%; PEF, peak expiratory flow; SD, standard deviation; CI, confidence interval; t-, total; m-, morning; e-, evening.

Figure 3

Absolute values for FEV₁ (A), FEV₃ (B), MEF50 (D), MEF25 (E), and MMEF (F), ratio values for FEV₁/FVC (C), FEV₃/FVC (G), MEF25/FVC (H), and MMEF/FVC (I) by age (N = 31, except N = 30 for PEF). Graphs were generated to illustrate characteristics of large- and small airway function values by age. FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; MEF50: forced expiratory flow at 50% of forced vital capacity; MEF25: forced expiratory flow at 75% of forced vital capacity; MMEF: forced expiratory flow between 25 and 75%; PEF, peak expiratory flow; SD, standard deviation; CI, confidence interval; t-, total; m-, morning; e-, evening.

Figure 4

Correlation of CV of pulmonary function variable values with age, height, weight, and BMI (total, morning, and evening) (N = 31, except N = 30 for PEF). A strong relationship between age and both large- [(A), r = 0.47, P = 0.0082 for tFEV₁] and small-airway (tMEF25, tMMEF, and tMMEF/FVC) function variables [(A), r ≥ 0.4, P < 0.05 for all]. tMEF50, tFEV₃/FVC, tMEF50/FVC, and tMEF25/FVC was weekly correlated to age [(A), 0.36 ≤ r ≥ 0.38, P < 0.05 for all], no significant relationships between height, weight, or BMI and both large- and small-airway function variables were found [(A), P > 0.05]. Similar correlation both in the morning and the evening was found (B). FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; MEF50, forced expiratory flow at 50% of forced vital capacity; MEF25, forced expiratory flow at 75% of forced vital capacity; MMEF, forced expiratory flow between 25 and 75%; PEF, peak expiratory flow; SD, standard deviation; CI, confidence interval; t-, total; m-, morning; e-, evening.

Figure 5

Correlation of diurnal variation of pulmonary function variable values with age, height, weight, and BMI (N = 30). A strong relationship between age and FEV₁ as well as FEV₃ (r = 0.47, P = 0.0109 for FEV₁ and r = 0.43, P = 0.0215 for FEV₃) was found. There was no significance between age and FVC, PEF, MEF50, MEF25, and MMEF (P > 0.05 for all). No significant correlations were also found among height, weight, or BMI and both large- and small-airway function variables (P > 0.05 for all). BMI, body mass index; FVC, forced vital capacity; FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; MEF50, forced expiratory flow at 50% of forced vital capacity; MEF25, forced expiratory flow at 75% of forced vital capacity; MMEF, forced expiratory flow between 25 and 75%; PEF, peak expiratory flow.

Figure 6

Simple linear regression of diurnal variation of FEV₁ and FEV₃ with age in non-smoking healthy adults (N = 30). Diurnal variation of FEV₁ and FEV₃ were positively related to age in non-smoking healthy adults (P = 0.0109, df = 29 for FEV₁ and P = 0.0215, df = 29 for FEV₃). FEV₁, forced expiratory volume in 1 s; FEV₃, FEV in 3 s; df , degree of freedom.