Preserved ratio impaired spirometry linked with multimorbidity, increased mortality

Preserved ratio impaired spirometry is a common lung function trait associated with breathlessness, multimorbidity and increased mortality risk, researchers reported in The Lancet Respiratory Medicine.

Preserved ratio impaired spirometry, also known as PRISm, is defined as FEV₁ of less than 80% predicted, despite a normal or preserved FEV₁/FVC ratio.

“[Preserved ratio impaired spirometry] is hypothesized to be a precursor of COPD, which if proven, could represent a promising target for interventions to prevent COPD, a leading cause of global mortality,” Daniel H. Higbee, MBBS, from the Medical Research Council Integrative Epidemiology Unit at the University of Bristol Medical School, U.K., and colleagues wrote. “Imaging studies suggest that [preserved ratio impaired spirometry] might be associated with a degree of airway disease and emphysema that might affect progression to COPD. Findings from other cohort studies have reported an association between [preserved ratio impaired spirometry] and respiratory symptoms, increased health care utilization, comorbidities such as obesity, diabetes, cardiac disease and increased overall mortality.”

Previous research was based on relatively small and selective cohorts with short-follow-up. Higbee and colleagues aimed to determine the prevalence, risk factors, clinical implications and mortality of low-scoring preserved ratio impaired spirometry in a large population of adults.

Among 351,874 UK Biobank participants with a median follow up of 9 years, 38,639 (mean age, 56.4 years; 55.4% women) had preserved ratio impaired spirometry at baseline.

Preserved ratio impaired spirometry was strongly associated with obesity (OR = 2.4; 95% CI, 2.26-2.55; P < .0001), current smoking (OR = 2; 95% CI, 1.91-2.14; P < .0001) and patient-reported physician-diagnosed asthma (OR = 1.76; 95% CI, 1.66-1.88; P < .0001), according to the results. In addition, female sex, overweight, trunk fat mass and trunk fat percentage were identified as other risk factors.

The researchers reported that preserved ratio impaired spirometry was strongly associated with symptoms and comorbidities, including breathlessness (adjusted OR = 2; 95% CI, 1.91-2.14; P < .0001) and cardiovascular disease (aOR = 1.71; 95% CI, 1.64-1.83; P < .0001).

Twelve percent of 1,973 participants with preserved ratio impaired spirometry at baseline had airflow obstruction consistent with COPD at follow-up, according to longitudinal analysis.

Preserved ratio impaired spirometry was also associated with increased risk for all-cause mortality (aHR = 1.61; 95% CI, 1.53-1.69; P < .0001) compared with control participants with FEV₁ of 80% or more predicted and FEV₁/FVC ratio of 0.70 or higher.

“[Preserved ratio impaired spirometry] is associated with breathlessness, diabetes, cardiovascular comorbidities and death event after adjustment for shared risk factors including smoking. [Preserved ratio impaired spirometry] is often a transient state with 50% of participants reverting to normal lung function and 12% progressing to airflow obstruction during a 9-year period. Although [preserved ratio impaired spirometry] is strongly associated with asthma, BMI and smoking, these factors do not seem to entirely account for this lung function trait and the mechanisms remain unclear,” the researchers wrote.

Further research on the genetic, structural and functional pathophysiology of preserved ratio impaired spirometry is required to identify individuals at risk for abnormal lung function abnormalities, according to the researchers.

“Our analysis is an example of the power of large population cohorts like UK Biobank in allowing us to more accurately describe the epidemiology and implications of abnormal lung function by accounting for sample size and selection bias,” Higbee said in a press release from the University of Bristol.

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