Trends and mortality effects of vitamin A deficiency in children in 138 low-income and middle-income countries between 1991 and 2013: a pooled analysis of population-based surveys.
BACKGROUND
Vitamin A deficiency is a risk factor for blindness and for mortality from measles and diarrhoea in children aged 6-59 months. We aimed to estimate trends in the prevalence of vitamin A deficiency between 1991 and 2013 and its mortality burden in low-income and middle-income countries.


METHODS
We collated 134 population-representative data sources from 83 countries with measured serum retinol concentration data. We used a Bayesian hierarchical model to estimate the prevalence of vitamin A deficiency, defined as a serum retinol concentration lower than 0·70 μmol/L. We estimated the relative risks (RRs) for the effects of vitamin A deficiency on mortality from measles and diarrhoea by pooling effect sizes from randomised trials of vitamin A supplementation. We used information about prevalences of deficiency, RRs, and number of cause-specific child deaths to estimate deaths attributable to vitamin A deficiency. All analyses included a systematic quantification of uncertainty.


RESULTS
In 1991, 39% (95% credible interval 27-52) of children aged 6-59 months in low-income and middle-income countries were vitamin A deficient. In 2013, the prevalence of deficiency was 29% (17-42; posterior probability [PP] of being a true decline=0·81). Vitamin A deficiency significantly declined in east and southeast Asia and Oceania from 42% (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) also occurred. In 2013, the prevalence of deficiency was highest in sub-Saharan Africa (48%; 25-75) and south Asia (44%; 13-79). 94 500 (54 200-146 800) deaths from diarrhoea and 11 200 (4300-20 500) deaths from measles were attributable to vitamin A deficiency in 2013, which accounted for 1·7% (1·0-2·6) of all deaths in children younger than 5 years in low-income and middle-income countries. More than 95% of these deaths occurred in sub-Saharan Africa and south Asia.


CONCLUSIONS
Vitamin A deficiency remains prevalent in south Asia and sub-Saharan Africa. Deaths attributable to this deficiency have decreased over time worldwide, and have been almost eliminated in regions other than south Asia and sub-Saharan Africa. This new evidence for both prevalence and absolute burden of vitamin A deficiency should be used to reconsider, and possibly revise, the list of priority countries for high-dose vitamin A supplementation such that a country's priority status takes into account both the prevalence of deficiency and the expected mortality benefits of supplementation.


BACKGROUND
Bill & Melinda Gates Foundation, Grand Challenges Canada, UK Medical Research Council.
Department of Health Statistics and Information Systems, World Health Organization, Geneva, Switzerland.
Gretchen A
GA
Stevens
MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
James E
JE
Bennett
MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
Quentin
Q
Hennocq
Department of Global Health and Population, Harvard T H Chan School of Public Health, Boston, MA, USA.
Yuan
Y
Lu
Micronutrient Initiative, Ottawa, Ontario, Canada.
Luz Maria
LM
De-Regil
Department of Nutrition for Health and Development, World Health Organization, Geneva, Switzerland.
Lisa
L
Rogers
Department of Global Health and Population, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA.
Goodarz
G
Danaei
MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK.
Guangquan
G
Li
Department of Infectious Disease Epidemiology, Division of Infectious Disease Control and Department of Health Statistics, Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway.
Richard A
RA
White
School of Computer Science & Heinz College, Carnegie Mellon University, Pittsburgh, PA, USA.
Seth R
SR
Flaxman
Independent Consultant, Geneva, Switzerland.
Sean-Patrick
SP
Oehrle
Mathematica Policy Research, Cambridge, MA, USA.
Mariel M
MM
Finucane
PROESA-Research Center for Social Protection and Health Economics, Universidad Icesi, Cali, Colombia.
Ramiro
R
Guerrero
Center of Excellence in Women and Child Health, Aga Khan University, Karachi, Pakistan; Centre for Global Child Health, Hospital for Sick Children, Toronto, Ontario, Canada.
Zulfiqar A
ZA
Bhutta
Universidad Autónoma de Santo Domingo, Santo Domingo, Dominican Republic.
Amarilis
A
Then-Paulino
Department of Global Health and Population, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Nutrition, Harvard School of Public Health, Boston, MA, USA.
Wafaie
W
Fawzi
Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA.
Robert E
RE
Black
MRC-PHE Centre for Environment and Health, School of Public Health, Imperial College London, London, UK. Electronic address: majid.ezzati@imperial.ac.uk.
Majid
M
Ezzati
D001499:Bayes Theorem; D002648:Child; D046688:Child Mortality / Q000639:trends*; D002675:Child, Preschool; D003906:Developing Countries / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007223:Infant; D015995:Prevalence; D014802:Vitamin A Deficiency / Q000453:epidemiology* / Q000401:mortality