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Background. Malnutrition in preschool children, usually measured as wasting, is widely used to assess possible needs for emergency humanitarian interventions in areas vulnerable to drought, displacement, and related causes of food insecurity. The extent of fluctuations in wasting by season, year-to-year, and differential effects by livelihood group, need to be better established as a basis for interpretation together with ways of presenting large numbers of survey results to facilitate interpretation.

Objective. To estimate levels of and fluctuations in wasting prevalences in children from surveys conducted in arid and semiarid areas of the Greater Horn of Africa according to livelihood (pastoral, agricultural, mixed, migrant), season or month, and year from 2000 to 2006.

Methods. Results from around 900 area-level nutrition surveys (typical sample size, about 900 children) were compiled and analyzed. These surveys were carried out largely by nongovernmental organizations, coordinated by UNICEF, in vulnerable areas of Eritrea, Ethiopia, Kenya, Somalia, Southern Sudan, and Uganda. Demographic and Health Survey (DHS) and Multiple Indicator Cluster Survey (MICS) data were used for comparison. Data were taken from measurements of children 0 to 5 years of age (or less than 110 cm in height).

Results. Among pastoral child populations, the average prevalence of wasting (< -2 SD weight-for-height) was about 17%, 6-7 percentage points higher than the rates among agricultural populations or populations with mixed livelihoods. Fluctuations in wasting were greater among pastoralists during years of drought, with prevalences rising to 25% or higher; prevalences among agricultural populations seldom exceeded 15%. This difference may be related to very different growth patterns (assessed from DHS and UNICEF/MICS surveys), whereby pastoral children typically grow up thinner but taller than children of agriculturalists. Wasting peaks are seen in the first half of the year, usually during the dry or hunger season. In average years, the seasonal increase is about 5 percentage points. Internally displaced people and urban migrants have somewhat higher prevalence rates of wasting. Year-to-year differences are the largest, loosely correlated with drought at the national level but subject to local variations.

Conclusions. Tracking changes in wasting prevalence over time at the area level-e.g., with time-series graphical presentations facilitates interpretation of survey results obtained at any given time. Roughly, wasting prevalences exceeding 25% in pastoralists and 15% in agriculturalists (taking account of timing) indicate unusual malnutrition levels. Different populations should be judged by population-specific criteria, and invariant prevalence cutoff points avoided; interpretation rules are suggested. Survey estimates of wasting, when seen in the context of historical values and viewed as specific to different livelihood groups, can provide useful timely warning of the need for intervention to mitigate developing nutritional crises.