“…A summary of these studies was drawn up, listing the author and year of publication, country, study design, and data collection method, aim, subjects, sample size, instruments used, hearing-aid (Hartley et al, 2010;Ham et al, 2014;Hickson et al, 2014), and only two in Asia (Chang et al, 2009;Mizutari et al, 2013). The majority of the studies were cross-sectional studies, three were cohort studies (Collins et al, 2007;Fischer et al, 2011;Mizutari et al, 2013), two were randomized controlled trials (Yueh et al, 2001;Saunders et al, 2009), and one was a longitudinal study (Humes et al, 2002).…”