Environmental - lifestyle related factors

Abstract

The prevalence of gastro-oesophageal reflux disease (GORD) has been increasing worldwide. This increase is likely associated with the increased prevalence of obesity, the ageing of the population and the decreased prevalence of Helicobacter pylori (Hp) infection. These different environmental factors interact with GORD pathogenesis in a potentially negative way. Oesophago-gastric junction (OGJ) competence, oesophageal clearance mechanisms and reflux causticity are involved in GORD pathophysiology. Obesity alters GORD pathogenesis by disrupting the OGJ and increasing intragastric pressure. Additionally, the number of transient lower oesophageal sphincter relaxations is potentially increased in obese patients. The potential effect of obesity on oesophageal peristalsis and the implication of impaired oesophageal clearance in GORD pathogenesis are still to establish. Ageing also plays an important role in GORD pathogenesis by decreasing lower oesophageal sphincter pressure and impairing oesophageal clearance. However a link between these abnormalities and an increased acid oesophageal exposure has not yet been demonstrated in the elderly. The role of H. pylori and its eradication remain controversial. The type of Hp gastritis may explain the controversial effect. Hp with antral predominant gastritis is responsible for an increased gastric acid secretion and thus promotes GORD. On the opposite spectrum, Hp with diffuse gastritis induces a gastric atrophy and in this particular case, the Hp eradication may restore acid secretion and lead to a more caustic refluxate in patients with predisposing conditions for GORD. The association of GORD and the type of Hp gastritis remains to be confirmed.

Figure 1

The environmental factors interact with the different mechanisms involved in GERD pathogenesis. Obesity alters esophago-gastric junction (EGJ) integrity, esophageal peristalsis and increases intra-gastric pressure. Age modifies EGJ integrity and impairs esophageal clearance by altering esophageal peristalsis and decreasing saliva secretion. Eating habits and medications decrease lower esophageal sphincter pressure (LES), increase the number of transient LES relaxations and delay gastric emptying. Helicobacter pylori modifies acid gastric secretion.

Figure 2

Increased prevalence of Obesity (left panel) and GERD (right panel) among US adults. The age-adjusted prevalence of overweight (BMI 25-30 kg/m², black diamond, dashed line), obesity (BMI > 30 kg/m², white square, black line) and extremely obesity (BMI > 40 kg/m², black triangle, black line) increased from 1960 to 2006. This survey includes subjects aged from 20 to 74 years (source: Department of Health and Human Services. Centers for Disease Control and Prevention.http://www.cdc.gov/nchs/data/hestat/overweight/overweight_adult.htm [30]). The time trends of hospitalization for gastro-esophageal reflux disease also increased in the US Department of Vetrans Affairs from 1970 to 1995 [31].