Associations between vitamin D and pulmonary function in chronic spinal cord injury.

CONTEXT/OBJECTIVE: Individuals with chronic spinal cord injury (SCI) have an increased risk of morbidity and mortality attributable to respiratory diseases. Previous studies in non-SCI populations suggest that vitamin D may be a determinant of respiratory health. Therefore, we sought to assess if lower vitamin D levels were associated with decreased pulmonary function in persons with chronic SCI. DESIGN: Cross-sectional study. SETTING: Veterans Affairs Medical Center. PARTICIPANTS: 312 participants (260 men and 52 women) with chronic SCI recruited from VA Boston and the community participating in an epidemiologic study to assess factors influencing respiratory health. METHODS: Participants provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma 25-hydroxyviatmin D and spirometric measures of pulmonary function. OUTCOME MEASURES: Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC. RESULTS: Adjusted and unadjusted for a number of confounders, there was no significant association between plasma vitamin D levels and FEV1, FVC, or FEV1/FVC. For example, in fully adjusted models, each 10 ng/ml increase in vitamin D was associated with a 4.4 ml (95%CI -64.4, 73.2, P = 0.90) ml change in FEV1. Conclusion: There was no significant cross-sectional association between plasma vitamin D and FEV1, FVC, or FEV1/FVC in this cohort of individuals with chronic SCI.

Vitamin D, diet, and lifestyle in a chronic SCI population.

STUDY DESIGN: Cross-sectional study. OBJECTIVES: Determine dietary, lifestyle, and clinical factors associated with plasma 25-hydroxyvitamin D [25(OH)D] levels in persons with chronic spinal cord injury (SCI). SETTING: Veterans Affairs Medical Center in Boston, MA. METHODS: 174 participants completed food frequency and health questionnaires, provided a blood sample, and underwent dual x-ray absorptiometry (DXA) to assess %total body fat. Linear regression models were used to assess cross-sectional associations of personal, lifestyle, and nutritional factors with plasma 25(OH)D. RESULTS: Independent factors positively associated with higher plasma 25(OH)D included vitamin D intake, age, hours of planned exercise, female sex, white race, wine consumption, and if a never or former smoker. The most important predictor of 25(OH)D was supplement intake. The majority of subjects (98.9% for vitamin D and 74.1% for calcium) did not meet the recommended daily allowance for adults from their diet alone. Level and completeness of SCI, injury duration, mobility, %total body fat, time outside, and comorbid diseases were not associated with plasma 25(OH)D. CONCLUSIONS: Plasma 25(OH)D level in chronic SCI is not associated with clinical factors specific to SCI such as injury level and completeness, injury duration, and mobility mode, but related to supplement intake and other lifestyle factors.

Plasma Leptin and Reduced FEV1 and FVC in Chronic Spinal Cord Injury.

BACKGROUND: Adipose tissue produces leptin, which is pro-inflammatory, and adiponectin, which has anti-inflammatory properties. Participants with chronic spinal cord injury (SCI) have increased body fat and are at increased risk for respiratory illness. OBJECTIVE: To assess the associations between leptin and adiponectin with pulmonary function in a chronic SCI cohort. DESIGN: Cross-sectional study. SETTING: Veterans Affairs Medical Center. PARTICIPANTS: A total of 285 participants (237 men and 48 women) with chronic SCI with mean (standard deviation) injury duration 17.8 (13.2) years from the VA Boston and the community participating in an epidemiologic study assessing factors associated with respiratory health. METHODS: Participants (24.6% cervical American Spinal Injury Association Impairment Scale (AIS) level A, B, and C; 33.6% other AIS A, B, and C; 41.8% AIS D) provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma leptin and adiponectin with spirometric measures of pulmonary function adjusted for age, race, gender, and height. Level and severity of SCI, mobility mode, body mass index, smoking, chronic obstructive pulmonary disease, asthma, chest injury history, laboratory batch, and other potential confounders were also considered. MAIN OUTCOME MEASUREMENTS: forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC. RESULTS: There was a statistically significant inverse relationship between plasma leptin assessed in quartiles or as a continuous covariate with FEV1 and FVC. In fully adjusted models, each interquartile range (16,214 pg/mL) increase in leptin was associated with a significant decrease in FEV1 (-93.1 mL; 95% confidence interval = -166.2, -20.0) and decrease in FVC (-130.7 mL; 95% confidence interval = -219.4, -42.0). There were no significant associations between leptin and FEV1/FVC or between plasma adiponectin with FEV1, FVC, or FEV1/FVC. CONCLUSION: Plasma leptin in individuals with chronic SCI is inversely associated with FEV1 and FVC, independently of SCI level and severity and other covariates. This finding suggests that plasma leptin may contribute to reduced pulmonary function in chronic SCI. LEVEL OF EVIDENCE: II.

Associations between vitamin D, adiposity, and respiratory symptoms in chronic spinal cord injury.

Context/Objective Persons with chronic spinal cord injury (SCI) have an increased risk of respiratory-related morbidity and mortality and chronic respiratory symptoms are clinical markers of future respiratory disease. Therefore, we sought to assess potentially modifiable factors associated with respiratory symptoms, with a focus on circulating vitamin D and measures of body fat. Design Cross-sectional study. Setting Veterans Affairs Medical Center. Participants Three hundred forty-three participants (282 men and 61 women) with chronic SCI participating in an epidemiologic study to assess factors influencing respiratory health recruited from VA Boston and the community. Methods Participants provided a blood sample, completed a respiratory health questionnaire, and underwent dual x-ray absorptiometry (DXA) to assess % body fat. Logistic regression was used to assess cross-sectional associations between respiratory symptoms and plasma vitamin D and measures of body fat with adjustment for a number of potential confounders. Outcome Measures Chronic cough, chronic phlegm, any wheeze, persistent wheeze. Results After adjustment for a number of confounders (including smoking), participants with greater %-android, gynoid, trunk, or total body fat had increased odds ratios for any wheeze and suggestive associations with persistent wheeze, but not with chronic cough or phlegm. Vitamin D levels were not associated with any of the respiratory symptoms. Conclusion Increased body fat, but not vitamin D, was associated with wheeze in chronic SCI independent of a number of covariates.

FEV1 and FVC and systemic inflammation in a spinal cord injury cohort.

BACKGROUND: Systemic inflammation has been associated with reduced pulmonary function in individuals with and without chronic medical conditions. Individuals with chronic spinal cord injury (SCI) have clinical characteristics that promote systemic inflammation and also have reduced pulmonary function. We sought to assess the associations between biomarkers of systemic inflammation with pulmonary function in a chronic SCI cohort, adjusting for other potential confounding factors. METHODS: Participants (n = 311) provided a blood sample, completed a respiratory health questionnaire, and underwent spirometry. Linear regression methods were used to assess cross-sectional associations between plasma C-reactive protein (CRP) and interleukin-6 (IL-6) with forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC. RESULTS: There were statistically significant inverse relationships between plasma CRP and IL-6 assessed in quartiles or continuously with FEV1 and FVC. In fully adjusted models, each interquartile range (5.91 mg/L) increase in CRP was associated with a significant decrease in FEV1 (-55.85 ml; 95% CI: -89.21, -22.49) and decrease in FVC (-65.50 ml; 95% CI: -106.61, -24.60). There were similar significant findings for IL-6. There were no statistically significant associations observed with FEV1/FVC. CONCLUSION: Plasma CRP and IL-6 in individuals with chronic SCI are inversely associated with FEV1 and FVC, independent of SCI level and severity of injury, BMI, and other covariates. This finding suggests that systemic inflammation associated with chronic SCI may contribute to reduced pulmonary function.

Airflow limitations in pregnant women suspected of sleep-disordered breathing.

BACKGROUND AND AIM: Pregnancy physiology may predispose women to the development of airflow limitations during sleep. The goal of this study was to evaluate whether pregnant women suspected of sleep-disordered breathing (SDB) are more likely to have airflow limitations compared to non-pregnant controls. METHODS: We recruited pregnant women referred for polysomnography for a diagnosis of SDB. Non-pregnant female controls matched for age, body mass index (BMI), and apnoea-hypopnoea index (AHI) were identified from a database. We examined airflow tracings for changes in amplitude and shape. We classified airflow limitation by (a) amplitude criteria defined as decreased airflow of > or =10 s without desaturation or arousal (FL 10), or decreased airflow of any duration combined with either 1-2% desaturation or arousal, (FL 1-2%); and (b) shape criteria defined as the presence of flattening or oscillations of the inspiratory flow curve. RESULTS: We identified 25 case-control pairs. Mean BMI was 44.0±6.9 in cases and 44.1±7.3 in controls. Using shape criteria, pregnant women had significantly more flow-limited breaths throughout total sleep time (32.4±35.8 vs. 9.4±17.9, p<0.0001) and in each stage of sleep (p<0.0001) than non-pregnant controls. In a subgroup analysis, pregnant women without a diagnosis of obstructive sleep apnoea (OSA) who had an AHI <5 had similar findings (p<0.0001). There was no difference in airflow limitation by amplitude criteria between pregnant women and controls (p=0.22). CONCLUSIONS: Pregnant women suspected of OSA have more frequent shape-defined airflow limitations than non-pregnant controls, even when they do not meet polysomnographic OSA criteria.