I have a dataset from a prevalence study. The prevalence study was not run every year so for example I have data from 2001, 2003, 2004, 2006, 2007, 2008, 2010, 2011, 2013, 2015, 2016. 2018 and I want to see if year is a "risk factor" for increasing prevalence. As I have missing years would it be appropriate to categorise the years in to 5 year bins so for example 2000-2004, 2005-2009, 2010-2014, 2015-2019 and that way I'd have three years worth of data within each category.