What are the risk factors for Helicobacter pylori infection?

Risk Factors for Helicobacter pylori Infection

H. pylori infection is primarily acquired during childhood through person-to-person transmission, with the strongest risk factors being low socioeconomic status, household crowding, poor sanitation, and lack of access to clean water during childhood. 1, 2, 3

Socioeconomic and Environmental Risk Factors

Childhood Living Conditions

• Childhood socioeconomic status is the most powerful predictor of H. pylori infection in adulthood, with infection rates strongly linked to living conditions during the first decade of life rather than current adult circumstances. 3
• Absence of a fixed hot-water supply during childhood increases infection risk significantly (p = 0.0005), as does domestic crowding (p = 0.0005). 3
• Poor hygiene and inadequate sanitation practices during childhood facilitate transmission among family members and remain the dominant risk factors even in recently infected children. 4, 5
• Contaminated water sources, particularly untreated well water, represent an important transmission route, especially in regions where water sanitation is suboptimal. 6

Household Crowding and Bed-Sharing

• Bed-sharing between children and parents dramatically increases infection risk, with odds ratios of 2.29 (95% CI 1.21-4.32) for sharing one to two nights per week, and 2.95 (95% CI 1.35-6.45) for more frequent bed-sharing. 4
• The number of children living in the household is independently associated with H. pylori infection (p = 0.004), reflecting increased person-to-person transmission opportunities. 3
• Household density and overcrowding remain significant risk factors even after adjusting for age and social class. 4

Demographic and Geographic Risk Factors

Race, Ethnicity, and Immigration Status

• Non-White race and ethnicity are established risk factors for both H. pylori infection and gastric cancer, though these factors reflect underlying socioeconomic disparities rather than genetic susceptibility. 1
• Immigration from high gastric cancer incidence countries (Eastern Europe, Andean Latin America, East Asia) substantially increases infection risk, with immigrants maintaining the high prevalence rates of their countries of origin. 1, 5
• In the United States, Asian, Hispanic, Black, and Native American populations have significantly elevated infection rates compared to non-Hispanic White populations. 1

Age and Cohort Effects

• In developed countries, infection prevalence increases with age due to a "cohort effect"—older generations acquired infection during childhood when sanitation was poorer, with rates ranging from 9% in those under 30 years to 67% in those over 70 years. 3, 7
• In developing countries, 60-90% of young people are already infected by adulthood, with most infections occurring during childhood. 7
• The incidence of new infections in adults is low (0.5-1.0% per year) in developed countries, confirming that childhood is the critical period for acquisition. 7

Familial and Intrafamilial Risk Factors

Family History and Clustering

• First-degree relatives of H. pylori-positive individuals have a two to three times increased risk of infection, and screening of adult household members should be considered when one family member tests positive. 1
• Intrafamilial clustering of H. pylori infection strongly supports person-to-person transmission within households, likely through oral-oral (vomitus, saliva) or fecal-oral routes. 6
• Family history of gastric cancer is an independent risk factor that warrants H. pylori screening even in younger individuals without symptoms. 1, 2

Occupational Risk Factors

Healthcare Workers

• Endoscopists face increased occupational risk, with infection probability correlating positively with the number of endoscopies performed. 7
• Iatrogenic transmission following endoscopy is the only proven mode of transmission outside person-to-person contact. 6
• In Poland, endoscopists show 75% seroprevalence compared to 59% in non-endoscopist medical staff, despite both groups having lower rates than the general population (70%). 7

Nutritional and Dietary Factors

• Adequate nutritional status, particularly frequent consumption of fruits and vegetables and vitamin C, appears protective against H. pylori infection. 6
• Food prepared under suboptimal conditions or exposed to contaminated water or soil increases infection risk. 6
• These dietary factors likely reflect broader socioeconomic conditions rather than direct protective mechanisms. 6

Important Clinical Considerations

High-Risk Populations Requiring Screening

• Opportunistic screening should be considered for individuals from high-risk ethnic groups (Asian, Hispanic, Black, Native American), immigrants from high gastric cancer incidence countries, and those with family history of gastric cancer or H. pylori infection. 1, 2
• The greatest benefit of H. pylori eradication occurs before development of gastric precancerous changes, making early identification of high-risk individuals critical. 1
• Screening between ages 20-40 years is recommended in high-risk populations to prevent progression from chronic gastritis to precancerous lesions. 1

Common Pitfalls

• Tobacco use and alcohol consumption have not been consistently demonstrated as risk factors for H. pylori infection in recent studies, despite earlier assumptions. 6
• Current adult socioeconomic status is a weaker predictor than childhood living conditions, so clinicians should specifically inquire about early-life circumstances when assessing risk. 3
• The infection is human-specific, and while domestic animals have been investigated as potential reservoirs, evidence for zoonotic transmission remains weak. 6