Can decreased lung function be used as a diabetes predictor?
The prevalence of type 2 diabetes is increasing in both developed and developing countries leading to major health and economic burdens for said countries. It is thought that this increase is likely due to increased obesity among populations, but other potential risk factors include impaired lung function. Previous clinical studies have proven that adults with diabetes typically have a lower forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) when compared with non-diabetic patients. Previous studies have also found that there is an inverse relationship between lung function of diabetes patients and blood glucose level, duration and severity of diabetes; independent of smoking status or obesity. Until now the association between lung capacity and type 2 diabetes has not been consistent. This study aims to assess the dose response relationship between FVC and FEV1 for type 2 diabetes patients.
This study looked at patients from Australia and China who were randomly selected using random cluster sampling. Patients then completed a questionnaire that included questions about age, sex, education, cigarette smoking, self-reported asthma, chronic obstructive pulmonary disease (COPD) and diabetes. Then blood pressure and body measurements were taken 3 times with the mean of the two closest recordings being used. Patients were classified as overweight if body mass index (BMI) was between 25-29.9, obesity was classified as BMI >30. Spirometry was used to obtain FEV1 and FVC; each patient completed two spirometry attempts while seated. The examination center then processed fasting blood specimens for glucose and lipid levels. Type 2 diabetes was defined using WHO criteria or through self-reported previously diagnosed diabetes. Metabolic Syndrome was defined by International Diabetes Federation (IDF) criteria. Patients with overlapping type 2 diabetes and metabolic syndrome were only defined as type 2 diabetes patients in the analysis of results.
Data analysis was performed after data collection was completed and the results are as follows. Continuous variables were assessed using the Kruskal-Wallis test, then categorical variables were assessed using the chi-squared test. Multiple linear regression models were used to assess the relationship between lung capacity measurements and linear variables, such as glucose and lipid profiles. An unconditional logistic model was used to show the relationship between lung capacity measurements and the odds ratios of diabetes or metabolic syndrome. The results of this study showed that there was a non-linear relationship between FEV1 and the risk of type 2 diabetes and metabolic syndrome, with a P<0.0001 in both Australian and Chinese populations. The FEV1 value that was associated with the lowest risk of diabetes and metabolic syndrome was above 2.7L. Below this threshold of 2.7 L the risk of developing diabetes decreased with an increase in FEV1 and above this threshold the odds ratio remained the same.
This study proved that there is a non-linear relationship between FEV1 and the risk of type 2 diabetes and metabolic syndrome, with a P<0.0001 in both Australian and Chinese populations. With that being said the risk of developing diabetes or metabolic syndrome is lowest with a FEV1 of 2.65-2.76 L. This information could be used as an indicator to check for diabetes and metabolic syndrome in patients with lower lung capacity. This is important because when patients are experiencing an exacerbation resulting in inhibited lung capacity, they are typically prescribed oral corticosteroids which would further increase blood glucose. Further studies should investigate the cost-benefit behind the use of this threshold (2.7L) in both Western and European populations.
- There is a non-linear relationship between FEV1 and the risk of type 2 diabetes and metabolic syndrome, with a P<0.0001.
- The FEV1 value that was associated with the lowest risk of diabetes and metabolic syndrome was above 2.7L.
- This 2.7L threshold of lung capacity could be used as an indicator to check for diabetes and metabolic syndrome in patients.
- There is a risk of increasing glucose levels with the treatment of oral corticosteroids.
Yu D, Chen T, Qin R, et al. Association between lung capacity and abnormal glucose metabolism: Findings from China and Australia. Clinical Endocrinology. doi: 10.1111/cen.13006; 139-148; doi:10.2337/dc15-0781.
Researched and prepared by Jennifer Zahn, Doctor of Pharmacy Candidate University Of South Florida College of Pharmacy, reviewed by Dave Joffe, BSPharm, CDE