Trends and mortality eff ects of vitamin A defi ciency in childrenudin 138 low-income and middle-income countries betweenud1991 and 2013: a pooled analysis of population-based surveys

摘要

Background Vitamin A defi ciency is a risk factor for blindness and for mortality from measles and diarrhoea inudchildren aged 6–59 months. We aimed to estimate trends in the prevalence of vitamin A defi ciency between 1991 andud2013 and its mortality burden in low-income and middle-income countries.udMethods We collated 134 population-representative data sources from 83 countries with measured serum retinoludconcentration data. We used a Bayesian hierarchical model to estimate the prevalence of vitamin A defi ciency, defi nedudas a serum retinol concentration lower than 0·70 μmol/L. We estimated the relative risks (RRs) for the eff ects of vitaminudA defi ciency on mortality from measles and diarrhoea by pooling eff ect sizes from randomised trials of vitamin Audsupplementation. We used information about prevalences of defi ciency, RRs, and number of cause-specifi c child deathsudto estimate deaths attributable to vitamin A defi ciency. All analyses included a systematic quantifi cation of uncertainty.udFindings In 1991, 39% (95% credible interval 27–52) of children aged 6–59 months in low-income and middle-incomeudcountries were vitamin A defi cient. In 2013, the prevalence of defi ciency was 29% (17–42; posterior probability [PP] ofudbeing a true decline=0·81). Vitamin A defi ciency signifi cantly declined in east and southeast Asia and Oceania from 42%ud(19–70) to 6% (1–16; PP>0·99); a decline in Latin America and the Caribbean from 21% (11–33) to 11% (4–23; PP=0·89)udalso occurred. In 2013, the prevalence of defi ciency was highest in sub-Saharan Africa (48%; 25–75) and south Asia (44%;ud13–79). 94 500 (54 200–146 800) deaths from diarrhoea and 11 200 (4300–20 500) deaths from measles were attributable toudvitamin A defi ciency in 2013, which accounted for 1·7% (1·0–2·6) of all deaths in children younger than 5 years in lowincomeudand middle-income countries. More than 95% of these deaths occurred in sub-Saharan Africa and south Asia.udInterpretation Vitamin A defi ciency remains prevalent in south Asia and sub-Saharan Africa. Deaths attributable toudthis defi ciency have decreased over time worldwide, and have been almost eliminated in regions other than southudAsia and sub-Saharan Africa. This new evidence for both prevalence and absolute burden of vitamin A defi ciencyudshould be used to reconsider, and possibly revise, the list of priority countries for high-dose vitamin A supplementationudsuch that a country’s priority status takes into account both the prevalence of defi ciency and the expected mortalityudbenefi ts of supplementation.