Risks of Mortality and Airflow Limitation in Japanese Individuals with Preserved Ratio Impaired Spirometry

Abstract

Rationale: Several Western studies have reported that participants with preserved ratio impaired spirometry (PRISm) have higher risks of airflow limitation (AFL) and death. However, evidence in East Asian populations is limited. Objectives: To investigate the relationship between PRISm and the risks of death and incident AFL in a Japanese population. Methods: A total of 3,032 community-dwelling Japanese participants aged ⩾40 years were seen in follow-up for a median of 5.3 years by annual spirometry examinations. Participants were classified into lung function categories at baseline as follows: normal spirometry (FEV₁/FVC ⩾0.70 and FEV₁ ⩾80% predicted), PRISm (⩾0.70 and <80%), AFL Global Initiative for Chronic Obstructive Lung Disease 1 (<0.70 and ⩾80%), and AFL Global Initiative for Chronic Obstructive Lung Disease 2-4 (<0.70 and <80%). Hazard ratios (HRs) and their 95% confidence intervals were computed using a Cox proportional hazards model. Measurements and Main Results: During the follow-up period, 131 participants died, 22 of whom died of cardiovascular disease, and 218 participants developed AFL. When examining the prognosis of each baseline lung function category, participants with PRISm had higher risks of all-cause death (HR, 2.20; 95% confidence interval, 1.35-3.59) and cardiovascular death (HR, 4.07; 1.07-15.42) than those with normal spirometry after adjusting for confounders. Moreover, the multivariable-adjusted risk of incident AFL was greater in participants with PRISm than in those with normal spirometry (HR, 2.48; 1.83-3.36). Conclusions: PRISm was associated with higher risks of all-cause and cardiovascular death and a greater risk of the development of AFL in a Japanese community.

Keywords: lung disease epidemiology; spirometry classification; spirometry mortality; spirometry statistics and numerical data.

Figure 1.

Kaplan-Meier plot of mortality by baseline lung function categories. *P < 0.05 versus normal spirometry. AFL = airflow limitation; GOLD = Global Initiative for Chronic Obstructive Lung Disease; PRISm = preserved ratio impaired spirometry.

Figure 2.

Transition of lung function categories from baseline to the follow-up period. AFL = airflow limitation; PRISm = preserved ratio impaired spirometry.

Figure 3.

The combined influence of PRISm at baseline and current smoking on (A) the risk of all-cause death and (B) the development of airflow limitation. The hazard ratio of all-cause death (A) was estimated in 2,509 participants without airflow limitation at baseline and adjusted for age, sex, smoking pack-years, body mass index, hypertension, diabetes mellitus, dyslipidemia, electrocardiogram abnormalities, history of cardiovascular disease, history of cancer, alcohol intake, and regular exercise. The hazard ratio of the development of airflow limitation (B) was estimated in 2,250 participants with normal spirometry or PRISm at baseline and adjusted for age, sex, smoking pack-years, body mass index, hypertension, diabetes mellitus, dyslipidemia, current drinking, regular exercise, and FEV₁ as a percentage of FVC at baseline. *P < 0.05 and ^†P < 0.20 versus the reference group (never or former smokers and participants with normal spirometry at baseline). AFL = airflow limitation; PRISm = preserved ratio impaired spirometry.