Reduced respiratory muscle strength and endurance in type 2 diabetes mellitus Leonello Fuso 1 * Dario Pitocco 2 Anna Longobardi 1 Francesco Zaccardi 2 Chiara Contu 1 Carmen Pozzuto 1 Salvatore Basso 1 Francesco Varone 1 Giovanni Ghirlanda 2 Raffaele Antonelli Incalzi 3 1 Respiratory Disease Unit, Catholic University, Rome, Italy 2 Diabetology Unit, Catholic University, Rome, Italy 3 Department of Geriatrics, Campus Biomedico University, Rome, Italy *Correspondence to: Leonello Fuso, Respiratory Disease Unit, Catholic University, Rome, Italy. E-mail: leofuso@rm.unicatt.it Abstract Background A restrictive lung function pattern is frequently observed in patients with diabetes mellitus (DM) and has been related to respiratory muscle dysfunction in type 1 DM or in mixed population. We aimed to verify whether such a relationship applies also to type 2 DM patients. Methods The respiratory muscle function was explored in 75 non-smoking patients with type 2 DM without pulmonary or cardiac diseases and compared with that of 40 healthy non-smoking control subjects matched by age and sex. Maximal inspiratory and expiratory pressures (MIP, MEP) and maximum voluntary ventilation (MVV), which reflect respiratory muscle strength and en- durance, respectively, were measured, and a complete respiratory function as- sessment was recorded. Results Patients were in stable metabolic conditions and had, on average, normal total lung capacity and diffusing lung capacity for carbon monox- ide. However, MIP and MVV were significantly reduced in comparison with those of control subjects. Both MIP/MEP and MVV significantly correlated with lung volumes and diffusing lung capacity for carbon monoxide. The multiple regression analysis identified age (beta coefficient = À0.238, p = 0.046), glycated haemoglobin (beta coefficient = À0.245, p = 0.047) and total lung capacity (beta coefficient = 0.430, p = 0.016) as independent correlates of MIP, whereas male sex (beta coefficient = 0.423, p = 0.004) and diabetic complications (beta coefficient = À0.248, p = 0.044) were in- dependent correlates of MVV. Conclusions In type 2 DM, respiratory muscle strength was reduced and significantly related to lung volumes and quality of metabolic control, whereas impaired endurance of respiratory muscles prevailed in patients with microvas- cular complications. Copyright © 2012 John Wiley & Sons, Ltd. Keywords respiratory muscle function; diabetes mellitus; metabolic control; microvascular complications; lung volumes Introduction Type 2 diabetes mellitus (DM) seems to be a risk factor for accelerated decline of lung function [1,2]. Indeed, in the Freemantle study, the decline of dynamic lung volumes was faster than expected and directly related to glycaemic exposure, as expressed by glycated haemoglobin (HbA 1c ) values [3]. The Atherosclerosis Risk in Communities Study recently confirmed that DM is associated with lower baseline values and accelerated decline of forced vital capacity (FVC) over 3 years [4]. Mechanisms likely explaining this RESEARCH ARTICLE Received: 15 April 2011 Revised: 15 December 2011 Accepted: 13 January 2012 Copyright © 2012 John Wiley & Sons, Ltd. DIABETES/METABOLISM RESEARCH AND REVIEWS Diabetes Metab Res Rev 2012; 28: 370–375. Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/dmrr.2284