Increased Risk of CTS (Strong Evidence)
Strong evidence supports that BMI and high hand/wrist repetition rate are associated with the increased risk of developing carpal tunnel syndrome (CTS).

BMI evaluated as a continuous variable was shown to be associated with development of CTS in four high quality (Armstrong, 2008; Bonfiglioli, 2013; Evanoff, 2014; Garg, 2012) and three moderate quality studies (Burt, 2011; Hlebs, 2014; Nordstrom, 1997). Only one moderate quality study (Goodson, 2014) found an insignificant result for the relationship between BMI and CTS. When evaluated as a categorical variable, five moderate quality studies (Becker, 2002; Burt, 2011; Burt, 2013; Coggon, 2013; Geoghegan, 2004) found a correlation between increasing BMI and development of CTS, while one high quality study (Hakim, 2002) and two moderate quality (Mondelli, 2006; Violante, 2007) studies found no significance.
High hand/wrist repetition rate at work was significantly associated to an increased risk of CTS by two high quality (Armstrong, 2008; Evanoff, 2014) and four moderate quality studies (Chiang, 1990; Coggon, 2013; Goodson, 2014; Silverstein, 1987).  In all studies, the hand/wrist repetition involved moderate to high hand forces.  One of the high quality studies (Armstrong, 2008) showed an insignificant association in two of the categories of repetition, but still showed a significant increase between the high and low quartile categories.