There was an association between those with longstanding diabetes using dipeptidyl peptidase 4 (DPP-4) inhibitors and a higher total score (rho -0.319, p = <0.01), score in the secretomotor domain (rho -0.248, p = 0.05), and score in the gastrointestinal domain (rho -0.333, p = <0.01), with a significantly different score in the gastrointestinal domain (Table 3). This evidence concerns the gene DPP4 and diabetes mellitus.