Casting a long shadow: the role of household crowding on Helicobacter pylori infection, and excess stomach cancer incidence among Māori and Pacific people in New Zealand (#73)
H. pylori has been linked with household crowding and is considered a necessary causal factor for non-cardia stomach cancer. Māori and Pacific peoples in New Zealand experience greater household crowding, H. pylori infection and stomach cancer incidence.
1) To summarise the association between household crowding and H. pylori and estimate the contribution of household crowding H. pylori seroprevalence by ethnicity
2) To estimate the excess stomach cancer incidence in Māori and Pacific that is attributable to H. pylori and smoking
A systematic review and meta-analysis was conducted to summarise the association between household crowding and H. pylori. The meta-analysis odds ratio was used to estimate the contribution of crowding to pooled H. pylori seroprevalence.
Rate ratios (RRs) for excess age-standardised Māori and Pacific stomach cancer incidence compared to European/Other were adjusted for H. pylori (restricting to the proportion seropositive), smoking (probabilistic bias analysis) and non-cardia subsite. Observed RRs were compared with adjusted RRs to give an ‘excess RR proportion’.
Persons experiencing greatest vs. the least household crowding had 1.73 (95% CI 1.48-2.03, n=28, I2=87%) greater odds of H. pylori infection, and this was greater for children exposed to household crowding (OR 2.06, CI: 1.53-2.77, n=19, I2=86%). Household crowding amongst children born 1971-85 contributed to 44% (95% CI: 32-54%) of Pacific, 36% (95% CI: 25-47%) of Māori, and 14% (95% CI: 9-20%) of European seroprevalence. Pooled average H. pylori seroprevalence was greatest among Pacific (62%), followed by Māori (35%) and European (18%).
H. pylori and smoking (to a lesser degree) contributed to more than half of the excess non-cardia stomach cancer among Māori (53-65%) and approximately eight-tenths of the excess non-cardia stomach cancer among Pacific (74-90%)
Household crowding is a major contributing factor to Māori and Pacific H. pylori seroprevalence; and the primary driver of excess non-cardia stomach cancer incidence among Māori and Pacific.