Lung Function Decline in Adult Asthmatics-A 10-Year Follow-Up Retrospective and Prospective Study

Abstract

Asthma may have an impact on lung function decline but conflicting results are reported in forced expiratory volume in one second (FEV₁) decline. We aimed to describe the changes in FEV₁ in lifelong non-smoking adult asthmatic outpatients during a 10-year follow-up comparing years 1-5 (1st period) with years 6-10 (2nd period) to assess factors affecting these changes. A total of 100 outpatients performed spirometry every 3 months during a 10-year survey. FEV₁/Ht³ slope values of the 2nd period reduced significantly respect to the 1st period (p < 0.0001). FEV₁ slopes of years 1-5 and 6-10 were inversely associated with FEV₁ at enrolment (p = 0.02, p = 0.01, respectively). Reversibility and variability FEV₁ showed a significant effect on the 1st period slopes (p = 0.01 and p < 0.04, respectively). Frequent exacerbators in the 1st year had steeper FEV₁/Ht³ slopes in the 1st period (p = 0.01). The number of subjects using higher doses of ICS was significantly lower at the 10th years respect to the 5th and the 1st year (p < 0.001, p = 0.003, respectively). This study shows that FEV₁ decline in treated adult asthmatics non-smokers, over 10-year follow-up, is not constant. In particular, it slows down over time, and is influenced by FEV₁ at enrolment, reversibility, variability FEV₁ and exacerbation score in the 1st year.

Keywords: FEV1 decline; asthma; exacerbation; inhaled steroids; reversibility.

Figure 1

Slope values of relationships between height-adjusted FEV₁ and time (L/m³/year), separately for years 1–5 and 6–10. Bars indicate (from the bottom to the top) 10th, 25th, 50th (median), 75th and 90th percentiles. Values below 10th and above 90th percentiles are plotted as circles. A significant difference was found (p < 0.0001, Wilcoxon test).

Figure 2

Relationship between the individual differences between the slope of the 6th–10th year period and slope of the 1st–5th year period (∆slope FEV₁/Ht³) and slope FEV₁ years 1–5. A significant inverse correlation was found (p < 0.0001, Spearman Rank Correlation).

Figure 3

Relationships between slope values of relationships between height-adjusted FEV₁ and time (L/m³/year) for years 1–5 (Panel A) and for years 6–10 (Panel B) and FEV₁ at enrolment (% of predicted). Both correlations were significant (p = 0.02 and p = 0.01, respectively, Spearman Rank Correlation).

Figure 4

Slope values of relationships between height-adjusted FEV₁ and time (L/m³/year) during years 1–5 and years 6–10, separately for subjects with or without FEV₁ reversibility at enrolment. Bars indicate (from the bottom to the top) 10th, 25th, 50th (median), 75th and 90th percentiles. Values below 10th and above 90th percentiles are plotted as circles. In years 1–5 subjects with FEV₁ reversibility at enrolment showed significantly lower slope values (p = 0.01, Mann–Whitney U-test). No significant effect of reversibility was observed on FEV₁ slopes for years 6–10.

Figure 5

Slope values of relationships between height-adjusted FEV₁ and time (L/m³/year) during years 1–5 and years 6–10, separately for groups of FEV₁ variability at 1st year. Bars indicate (from the bottom to the top) 10th, 25th, 50th (median), 75th and 90th percentiles. Values below 10th and above 90th percentiles are plotted as circles. In years 1–5 subjects with FEV₁ variability at 1st year showed significantly lower slope values (p < 0.04, Mann–Whitney U-test). No significant effect of variability was observed on FEV₁ slopes for years 6–10.

Figure 6

FEV₁ variability (in percent of predicted), separately for 1st, 5th, and 10th years. Bars indicate (from the bottom to the top) 10th, 25th, 50th (median), 75th, and 90th percentiles. Values below 10th and above 90th percentiles are plotted as circles. Significant differences were found between 1st and 5th years, between 1st and 10th years and between 5th and 10th years (Wilcoxon test).

Figure 7

Prevalence of subjects, for each inhaled corticosteroid (ICS) score during the follow-up period. A Scheme of 10th and 5th years (p < 0.0001, χ²), between 10th and 1st years (p = 0.003, χ²), and between 5th and 1st years (p < 0.02, χ²).