“…Inclusion criteria were the following: Caucasian subjects ≥ 18 years old, body mass index (BMI) ≥ 18.5 kg/m 2 , affected by functional chronic constipation associated to delayed intestinal transit time, supported by Roma IV criteria[8,26,28]. Exclusion criteria were the following: Subjects > 75 years old, IBS, pregnancy, significant comorbidities such as cardiac, respiratory, chronic renal insufficiency, anorectal and pelvic floor dysfunctions, metabolic/endocrine (diabetes mellitus, hypothyroidism, hypercalcaemia, panhypopituitarism), medications (opiates, antihypertensive agents, iron preparations, anti-epileptic drugs, tryciclic antidepressants, anticholinergics or dopaminergics), organic (extra-intestinal mass, colorectal cancer, ischaemic or surgical stenosis, anal fissure, anal strictures, inflammatory bowel disease, intestinal malabsorption and diverticular diseases), neurological (Parkinson disease, multiple sclerosis, paraplegia, autonomic neuropathy, chronic intestinal pseudo-obstruction, gastroparesis, Hirschsprung disease and stroke), past psychiatric disease, and myogenic (scleroderma, amyloidosis and myotonic dystrophy dermatomyositis)[2,21,26]. In addition, we also assessed a control group of 86 healthy subjects (sex, age and BMI matched), recruited from a population-based cohort study of 150 healthy subjects, which underwent routine clinical exams in our Institute to check their healthy status, after excluding the presence of a functional chronic constipation during the clinical interview.…”