Inhaled steroid has been the cornerstone in the treatment of asthma, which carries a huge patient population worldwide including Hong Kong. In general, the safety of long-term use of inhaled steroid has been well documented. Yet, long-term users of such treatment carry increased risk of complications like cataract. In particular, the exact association of inhaled steroid use and development of diabetes mellitus is not known, despite a clear causal relationship between oral steroid use and diabetes. Therefore this epidemiology study (based on questionnaire and blood tests) aims to investigate the effect of inhaled corticosteroid on the risk of diabetes, impaired glucose tolerance and insulin resistance in adults with asthma. The impact of this study is expected to affect the current practice of long-term use of inhaled corticosteroid especially among patients with asthma.