No mediating effects of glycemic control and inflammation on the association between vitamin D and lung function in the general population

Abstract

Background: Vitamin D deficiency is discussed to be associated with lung health. While former studies focused on subjects suffering from pulmonary diseases, we aimed to investigate the association of 25-hydroxy vitamin D [25(OH)D] with lung function in the general population and examined whether mediating effects of inflammation, glycemic control or renal function exist.

Methods: 1404 participants from the Study of Health in Pomerania with pulmonary function testing assessed by expiratory volume in 1 s (FEV₁), forced vital capacity (FVC), total lung capacity and Krogh index were used. Adjusted analysis of variance, linear regression models and mediation analyses were performed.

Results: Significant positive associations between 25(OH)D levels and FEV₁, FVC and Krogh index were found. Mediator analyses revealed no mediating effect of inflammation (fibrinogen), glycemic control (HbA1c) or renal function (eGFR) on associations with FEV₁ or FVC. With respect to Krogh-Index, the association to 25(OH)D was slightly mediated by fibrinogen with a proportion mediated of 9.7%.

Conclusion: Significant positive associations of 25(OH)D with lung function were revealed in a general population. The proposed mediating effects of inflammation, glycemic control and renal function on these relations were not confirmed. Further studies examining the causality of the association between 25(OH)D and lung function are necessary.

Keywords: FEV1; HbA1c; Inflammation; Krogh index; Lung function; Mediating effects; Vitamin D.