Interactions of diarrhea, pneumonia, and malnutrition in childhood: recent evidence from developing countries

Abstract

Purpose of review: This review highlights recent progress toward understanding complex interactions between diarrhea, pneumonia, and undernutrition among children in low-income and middle-income countries.

Recent findings: New studies parallel earlier reports that diarrhea and pneumonia impair children's growth and that underlying malnutrition is a major risk factor for these conditions. Episodes of diarrhea may predispose to pneumonia in undernourished children. Additional studies support breastfeeding and micronutrient supplementation for the prevention and control of diarrhea and pneumonia. Malnutrition may partially account for the reduced efficacy of oral rotavirus vaccines in low-income countries. Immunization of pregnant women against influenza also appears to reduce intrauterine growth retardation. Immunization of infants against Streptococcus pneumoniae may improve their growth. New genetic studies indicate that polymorphisms in apolipoprotein E or the leptin receptor modulate children's risk for diarrhea and Entamoeba histolytica infection, respectively, thereby linking two genes important for lipid metabolism to enteric infections.

Summary: Significant advances have been made in understanding the vicious cycle of malnutrition, diarrhea, and pneumonia in developing countries. Future challenges will be to translate this progress into effective and widely accessible public health measures.

Figure 1. Weight-for-age and occurrence of common infections in a Guatemalan child

Solid line represents child’s weight-for-age; dashed line represents expected weight-for-age; D, diarrhea; URI, upper respiratory illness; BC, bronchitis; BN, bronchopneumonia; FUO, fever of unknown origin; CONJ, conjunctivitis; T, thrush; CEL, cellulitis. Reproduced with permission [3].

Figure 2. Impact of acute (<7 days), prolonged (≥ 7 and <14 days), and persistent (≥14 days) diarrhea on childhood growth

Nutritional Z-scores (age-adjusted and sex-adjusted standard deviations above or below WHO/CDC medians) were compared 3 months before and after children’s first acute (n = 308), prolonged (n = 145), and persistent (n = 62) (a) Weight-for-height (WHZ) Z-scores declined significantly following persistent episodes, but not after episodes. acute or prolonged episodes. (b) Weight-for-age (WAZ) Z-scores decreased with all episode types and mean WAZ of children prior to acute diarrhea was significantly greater than mean WAZ prior to persistent diarrhea. (c) Height-forage (HAZ) Z-scores declined following acute and prolonged episodes, but not after persistent episodes. Mean HAZ prior to acute diarrhea was greater than mean HAZ prior to prolonged or persistent diarrhea. (Error bars indicate SEM; *P < 0.005, paired t-test of Z-scores before and after diarrhea; §P < 0.05, unpaired t-test of Z-scores prior to acute vs. prolonged, acute vs. persistent, or prolonged vs. persistent episodes). Reproduced with permission [6•].

Figure 3. Risk of acute lower respiratory infections in children from Ghana in relation to the number of days of diarrhea during (a) the preceding 14 days and (b) the preceding 28 days

Reproduced with permission [17].

Figure 4. Variation in early childhood diarrhea burdens in Fortaleza, Brazil by apolipoprotein E allele

Progressive reductions in diarrhea with apolipoprotein E (APOE) alleles 2, 3, and 4 (P = 0.03), linear-by-linear association; n = 246 alleles in 123 cohort children. Reproduced with permission [39].