Does Ramadan fasting affect expiratory flow rates in healthy subjects?

Objectives: To assess whether Ramadan fasting affects the expiratory flow rates in healthy subjects, and to know if these effects correlate to a change in other variables. Methods: This unmatched case-control longitudinal study includes 46 non-smoking healthy subjects who undertook lung function testing at the Aga Khan University, Pakistan. Expiratory flow rates and body mass were measured in 3 Islamic months, corresponding to November 2001 to January 2002. Results: There was a significant reduction in body mass in Ramadan compared to pre and post Ramadan. No significant changes in expiratory flows were seen during Ramadan as compared to the pre Ramadan period. However, forced expiratory flow rates at 75% of vital capacity (FEF75) and between 75% and 85% of vital capacity (FEF75-85) showed a significant increase in the post Ramadan period compared to Ramadan. Changes in FEF 75 were negatively correlated to changes in body mass between Ramadan and post Ramadan. Conclusion: This study shows that Ramadan fasting will not affect expiratory flow rates in healthy subjects. Post Ramadan values did show an increase in FEF 75 and FEF (75-85), possibly due to changes in body water and fat content. The reductions in body mass were most probably due to lack of nutrition and not dehydration as the fasts were performed in winter. Collection of reference values or early phase clinical trials measuring expiratory flow rates should not be affected by Ramadan fasting.