Table 1

Classification of exposures related to poor hygiene and infection

DefinitionTotal (45)Cohort (6)Cross-sectional (30)Case–control (9)
Home environmentWater and sanitation, garbage disposal, house cleaning, housing construction, endotoxins9261
Animal contactContact with pets, farm animals and cockroaches inside/outside the house345236
Contact with other childrenOvercrowding in home, day-care attendance and having older siblings226115
Early-life infectionAcute respiratory and gastrointestinal infections during infancy, worm infections11461
Demonstrated infectionIntestinal parasites or chronic viral or bacterial infections diagnosed by serology or stool sample214116
  • Numbers represent the number of studies that measured at least one exposure related to each category, even if the results were not published.