Association of the relative change in weight and body mass index with lung function in teenagers and adults with cystic fibrosis: Influence of gender and diabetes.

BACKGROUND: Nutritional status is a prognostic factor in cystic fibrosis. Prevention of nutritional impairment and weigh loss are major clinical objectives because they are associated with worsening of lung function and increased mortality.

OBJECTIVE: To identify a potential relationship of clinical nutrition parameters, and their relative changes, with lung function (FEV1%) in a cohort of adolescent and adult patients with CF.

METHODS: A retrospective analysis of 64 patients older than 14years. Weight, height, BMI, and lung function data were collected at a period of disease stability, both in the year of the first abnormal oral glucose tolerance test (OGTT) and in the previous year. Relative changes in weight and BMI, and their relationship with FEV1%, were determined by linear regression and ANOVA tests; influence of gender and diabetes was also assessed.

RESULTS: Mean age of the series (28 females and 36 males) was 26.8years. Normal glucose tolerance (NGT) was found in 26.7%, while 18.3% had diabetes without impaired fasting glucose (CFRD without FPG). Mean BMI was 20.32, with a mean weight of 53.53kg; 32.8% had BMI<18.5, and only 4.7% were overweight. Overall, a positive relative change in weight (≥6%) was associated with an increase in FEV1% (9.31%), as compared to those with a greater weight loss (at least 2%), who had a 12.09% fall in FEV1. Patients with CFRD without FPG had poorer lung function if they had a negative relative change in weight by at least 2% as compared to NGT.

CONCLUSIONS: In patients with CF, a relative weight gain is positively associated to FEV1%, while a relative weight loss of at least 2% has a significant negative impact on lung function.