The exact prevalence and incidence of achlorhydria are not known. One single-centre retrospective study of 3374 patients who underwent oesophagogastroduodenoscopy in Thailand found a prevalence of 0.53%. All patients with achlorhydria were over 45 years old and had gastrointestinal Helicobacter pyloriinfection.[21]Phaosawasdi K, Sritunyarat Y, Lopimpisuth C, et al. Prevalence of achlorhydria in an Asian population detected using Congo red staining during routine gastroscopy: 22 years' experience from a single centre. BMJ Open Gastroenterol. 2022 Aug;9(1):e000976.
https://pmc.ncbi.nlm.nih.gov/articles/PMC9422802
http://www.ncbi.nlm.nih.gov/pubmed/36008085?tool=bestpractice.com
Incidence rates of atrophic gastritis vary widely, ranging from 0% to 11% per year, with substantially higher rates observed in H pylori-positive compared with H pylori-negative people.[8]Shah SC, Piazuelo MB, Kuipers EJ, et al. AGA clinical practice update on the diagnosis and management of atrophic gastritis: expert review. Gastroenterology. 2021 Oct;161(4):1325-32.e7.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8740554
http://www.ncbi.nlm.nih.gov/pubmed/34454714?tool=bestpractice.com
[22]Kuipers EJ, Pérez-Pérez GI, Meuwissen SG, et al. Helicobacter pylori and atrophic gastritis: importance of the cagA status. J Natl Cancer Inst. 1995 Dec 6;87(23):1777-80.
http://www.ncbi.nlm.nih.gov/pubmed/7473834?tool=bestpractice.com
[23]Adamu MA, Weck MN, Gao L, et al. Incidence of chronic atrophic gastritis: systematic review and meta-analysis of follow-up studies. Eur J Epidemiol. 2010 Jul;25(7):439-48.
http://www.ncbi.nlm.nih.gov/pubmed/20585973?tool=bestpractice.com
The prevalence of atrophic gastritis and autoimmune gastritis increases with age.[8]Shah SC, Piazuelo MB, Kuipers EJ, et al. AGA clinical practice update on the diagnosis and management of atrophic gastritis: expert review. Gastroenterology. 2021 Oct;161(4):1325-32.e7.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8740554
http://www.ncbi.nlm.nih.gov/pubmed/34454714?tool=bestpractice.com
[24]Weck MN, Stegmaier C, Rothenbacher D, et al. Epidemiology of chronic atrophic gastritis: population-based study among 9444 older adults from Germany. Aliment Pharmacol Ther. 2007 Sep 15;26(6):879-87.
http://www.ncbi.nlm.nih.gov/pubmed/17767472?tool=bestpractice.com
Gastric atrophy is associated with intestinal metaplasia and carries a two- to threefold increased risk for gastric adenocarcinoma.[25]Carmel R. Prevalence of undiagnosed pernicious anemia in the elderly. Arch Intern Med. 1996 May 27;156(10):1097-100.
http://www.ncbi.nlm.nih.gov/pubmed/8638997?tool=bestpractice.com
Pernicious anaemia, a common cause of cobalamin deficiency, caused by auto-antibodies directed against intrinsic factor and/or parietal cells, affects >2% of people over the age of 60 years.[25]Carmel R. Prevalence of undiagnosed pernicious anemia in the elderly. Arch Intern Med. 1996 May 27;156(10):1097-100.
http://www.ncbi.nlm.nih.gov/pubmed/8638997?tool=bestpractice.com
In a population study of 9684 adults aged 50-74 years, parietal cell antibodies, detected by enzyme-linked immunosorbent assay (ELISA), were present in 20% of study participants.[26]Zhang Y, Weck MN, Schöttker B, et al. Gastric parietal cell antibodies, Helicobacter pylori infection, and chronic atrophic gastritis: evidence from a large population-based study in Germany. Cancer Epidemiol Biomarkers Prev. 2013 May;22(5):821-6.
http://cebp.aacrjournals.org/content/22/5/821.long
http://www.ncbi.nlm.nih.gov/pubmed/23456556?tool=bestpractice.com
The parietal cell antibodies are directed against hydrogen-potassium-stimulated adenosine triphosphatase (H+/K+ ATPase), the proton pump of the parietal cell.[27]Toh BH, Alderuccio F. Pernicious anemia. Autoimmunity. 2004 Jun;37(4):357-61.
http://www.ncbi.nlm.nih.gov/pubmed/15518059?tool=bestpractice.com
[28]Davidson RJ, Atrah HI, Sewell HF. Longitudinal study of circulating gastric antibodies in pernicious anaemia. J Clin Pathol. 1989 Oct;42(10):1092-5.
http://jcp.bmj.com/content/42/10/1092.long
http://www.ncbi.nlm.nih.gov/pubmed/2584410?tool=bestpractice.com