INTRODUCTION
Over the last decade non-alcoholic fatty liver disease (NAFLD) has become the most common chronic liver disease (CLD) in Western world. This liver disease is a clinical syndrome which consists of several liver disorders. It is defined by existence of steatosis in at least 5% of hepatocytes with no history of alcohol consumption or evidence of other CLD. The clinical-histologic phenotype of the disorder extends from benign non-alcoholic fatty liver (NAFL) to more severe non-alcoholic steatohepatitis (NASH). NASH is more progressive form that can lead to fibrosis and cirrhosis which consequently lead to liver transplantation or progress to hepatocellular carcinoma (HCC) (1-4) Today, NAFLD is acknowledged as a liver manifestation of metabolic syndrome (MetS). With NAFLD being part of MetS, it can be closely associated with unhealthy lifestyle. Studies have shown that changes in unhealthy lifestyle improve transaminase levels and NAFLD (5).
One of the most popular beverages in the world is coffee. Inarguably, drinking coffee is a cultural phenomenon with billions of cups consumed worldwide. In recent years, a lot of interest has been tempted in the overall beneficial effects regarding the coffee consumption in reducing total and cause specific morbidity and mortality. Coffee seems to benefit health in general, especially liver health (6-10). Some authors have published data about beneficial effects of coffee consumption in diabetes mellitus (7), while some other reported its usefulness in the context of fibrosis, cirrhosis, and HCC in chronic hepatitis C infected patients (8). Due to epidemic increase of type 2 diabetes mellitus (T2DM), obesity and MetS, around 25% of population has fatty liver disease. NAFLD is not only important due to liver-related complications (i.e. cirrhosis and HCC) but also it is important in the context of multisystem disease that is associated with cardiovascular diseases, chronic kidney disease and T2DM, as well as to some other chronic diseases. Therefore, the beneficial effect of coffee consumption could be of great clinical interest because coffee is easily available. Although according to meta-analysis by Shen H et al (9) about the beneficial effect of coffee consumption on progression of liver disease, its effect in NAFLD population is not unequivocally clear.
Poor health outcomes are also associated with inadequate sleep. Insomnia and short sleep duration have been linked with obesity, diabetes, hypertension, cardiovascular diseases, and depression. Mechanism of it lies in irregular habits in exercise and diet, decreased leptin, and modulation of hormones of hypothalamic-pituitary-adrenal system (11,12). Some reports had shown that short sleep duration was associated with NAFLD prevalence, while some other studies reported that that long sleep duration related to incident NAFLD (11-13). Thus, the relationship between NAFLD and sleep duration is still poorly defined.
Finally, cigarette smoking is an unhealthy habit that is associated with many diseases on numerous organs. This habit damages the antioxidant system which can have repercussions on numerous organs. Smoking is an acknowledged risk factor for developing MetS, which is risk factor for NAFLD development (16-18). It has been reported that smoking can increase the risk for fibrosis and cirrhosis in patients with viral hepatitis, but only a few studies have investigated the relationship between smoking and NAFLD (16-18).
According to this observations, our aim was to explore the association between coffee consumption, sleep duration and smoking status and the controlled attenuation parameter (CAP) and liver stiffness measurements (LSM) as the surrogate markers of liver steatosis and fibrosis in a large cohort of NAFLD patients in Mediterranean parts of Croatia.