Among adults with type 2 diabetes, the presence of preserved ratio impaired spirometry (PRISm) was significantly associated with increased risk of mortality and both macro- and microvascular complications, as well as increased mortality, based on data from more than 20,000 individuals.
Guochen Li, MD, of the Medical College of Soochow University, Suzhou, China, and colleagues wrote.
“A growing number of studies have demonstrated that impaired lung function and type 2 diabetes could trigger shared pathophysiological injuries, such as microangiopathy and chronic inflammation,” they said, but the potential role of PRISm as an early predictor of adverse outcomes in patients with type 2 diabetes has not been fully examined.
In a study published in the journal Chest, the researchers reviewed data from 20,047 individuals with type 2 diabetes in the UK Biobank, a population-based cohort of adults aged 37-73 years recruited between 2006 and 2010.
The main exposure was lung function based on spirometry. PRISm was defined as predicted forced expiratory volume per second (FEV1) less than 80%, with an FEV1/ forced vital capacity (FVC) ratio of at least 0.70. Individuals with normal spirometry (defined as predicted FEV1 ≥ 80% with an FEV1/FVC ratio ≥ 0.70) served as controls.
The primary outcomes were major complications of type 2 diabetes including macrovascular events (myocardial infarction, unstable angina, coronary heart disease [CHD], ischemic stroke, and any type of stroke), microvascular events (diabetic retinopathy and diabetic kidney disease) and mortality (all-cause, cardiovascular, and respiratory).
Overall, 16.9% of study participants (3385 patients) had obstructive spirometry and 22.6% (4521 patients) had PRISm. Compared with individuals with normal spirometry, those with PRISm were more likely to be current smokers, obese, and living in economically disadvantaged areas. Individuals with PRISm also were significantly more likely to be long-term patients with diabetes who were taking glucose-lowering or lipid-lowering drugs (P < .001 for all).
The median follow-up for each of the type 2 diabetes complications and mortality was approximately 12 years. Over this time, 5.0% of patients developed incident MI, 1.3% developed unstable angina, 15.6% had CHD, 3.5% had an ischemic stroke, and 4.7% had any type of stroke. As for microvascular events, 7.8% developed diabetic retinopathy and 6.7% developed diabetic kidney disease. A total of 2588 patients died during the study period (15.1%), including 544 from cardiovascular disease and 319 from respiratory disease.
PRISm was significantly associated with increased risk of each of the complications and mortality types. These associations persisted after adjusting for lifestyle and other factors. The fully adjusted hazard ratios for PRISm versus normal spirometry were 1.23 for MI, 1.23 for unstable angina, 1.21 for CHD, 1.38 for ischemic stroke, 1.41 for any type of stroke, 1.31 for diabetic retinopathy, and 1.38 for diabetic kidney disease. Adjusted HRs for mortality were 1.34, 1.60, and 1.56 for all-cause, cardiovascular, and respiratory mortality, respectively.
The researchers also found that adding PRISm to an office-based risk score significantly improved the risk classification and predictive power for type 2 diabetes complications with the exception of unstable angina and mortality. They found little evidence for an association with sex, smoking, or PRISm duration and any mortality types. However, in subgroup analyses by age, sex, and duration of diabetes, PRISm remained associated with increased risk of macrovascular and microvascular complications, as well as mortality.
Potential mechanisms for the association between PRISm and diabetes complications include the role of insulin resistance in the exacerbation of lung damage in patients with type 2 diabetes, the increased rate of supplemental oxygen use among individuals with PRISm, and the increased prevalence of pulmonary artery enlargement in the PRISm subjects, the researchers wrote.
The findings were limited by several factors including the prospective design, the homogeneous population of individuals primarily of British or Irish ancestry, and the exclusion of diabetic neuropathy from the analysis, the researchers noted.
However, the results were strengthened by the large cohort, use of professional spirometry, and relatively long follow-up. “The findings underscore the relevance of PRISm for prognostic classification in type 2 diabetes and its potential for optimizing prevention strategies in this condition,” they concluded.
The study was supported by the National Natural Science Foundation of China, Natural Science Foundation of Jiangsu Province, and the Priority Academic Program Development of Jiangsu Higher Education Institutions. The researchers reported no relevant financial relationships.
A version of this article first appeared on Medscape.com