2.2. Participants

Definitions of aging vary. The definition used when referring to the older population is individuals aged 60 years of age and older. This definition is in keeping with the World Health Organization formal definition of older age [28], however an age of 65 and older is mostly in keeping with a majority view of the terms ‘aged’, ‘older’, ‘elderly’, or ‘geriatric’. Our original intention was to use 65 as a cut-off, however many important studies of age-related manometry changes used sixty as age cut-off and for this reason we concluded to use 60 years of age. The comparator was human participants between 18 and 59 years of age.