2022-tafesse.pdf: “The effect of Universal Salt Iodization on cognitive test scores in rural India”, (2022-04-01; similar):
- This study investigates the impact of Universal Salt Iodization in early life on children’s test scores in rural India.
- The program raised basic numeracy and literacy skills for the pooled sample and overall literacy scores for girls.
- Children from poor households and those residing in, or near the major salt producing state, benefited more from the policy.
- Universal Salt Iodization has the potential of improving children’s cognition in other developing countries at a low cost.
This paper studies the impact of a large-scale public health intervention in early life on cognitive skills in childhood. Iodine deficiency is the most common predictor of brain damage globally which has prompted over 140 countries to implement Universal Salt Iodization. While small-scale interventions report positive effects of iodine supplementation on cognition, the causal impact of salt iodization at scale is unknown across low-income countries.
This study evaluates the effect of Universal Salt Iodization on cognitive test scores of school-aged children in rural India. I exploit exogenous variation in the timing of the exposure to the policy in early life, comparing children residing in naturally iodine sufficient and deficient districts over time, using a difference in differences strategy.
Exposure to the program increased basic numeracy and literacy skills by at least 2.4 percentage points and improved school progression. It further raised literacy scores by 6.1% of a standard deviation for girls. The effects on test scores are higher for poor children and for those residing in, or nearby, the major salt producing state where iodized salt consumption was lower at baseline.
This is the first study to show that a blanket fortification policy can deliver considerable, yet heterogeneous, improvements in cognition in the medium run in a developing country context.
[Keywords: universal salt iodization, iodine deficiency disorders, fetal origins, early life, cognitive skills, educational outcome]
“Cognitive Consequences Of Iodine Deficiency In Adolescence: Evidence From Salt Iodization In Denmark”, (2019-06-21; backlinks; similar):
Over the past three decades, many countries have introduced iodized salt policies to eradicate iodine deficiency. While it is well known that iodine deficiency in utero is detrimental to cognitive ability, little is known about the consequences of iodine deficiencies after birth.
This paper examines the impact of iodine deficiency in adolescence on cognitive performance. I identify the causal effect of iodine deficiency quasi-experimentally using the introduction of iodized salt in Denmark. Denmark went from a ban on iodized salt before 1998 to a mandate after 2001, making it an ideal national experiment.
Combining administrative records on high school grades over a 30-year period with geographic variation in initial iodine deficiency, I find that salt iodization increases the Grade Point Averages of high school students by 6–9% of a standard deviation. This improvement is comparable to the benefits of more standard school achievement policies and at much lower costs.
[Keywords: iodine deficiency, iodized salt, nutrition, human capital, health]
“Small-quantity, lipid-based nutrient supplements provided to women during pregnancy and 6 mo postpartum and to their infants from 6 mo of age increase the mean attained length of 18-mo-old children in semi-urban Ghana: a randomized controlled trial”, (2016; backlinks; similar):
Background: Childhood stunting usually begins in utero and continues after birth; therefore, its reduction must involve actions across different stages of early life.
Objective: We evaluated the efficacy of small-quantity, lipid-based nutrient supplements (SQ-LNSs) provided during pregnancy, lactation, and infancy on attained size by 18 mo of age.
Design: In this partially double-blind, individually randomized trial, 1320 women at ≤20 wk of gestation received standard iron and folic acid (IFA group), multiple micronutrients (MMN group), or SQ-LNS (LNS group) daily until delivery, and then placebo, MMNs, or SQ-LNS, respectively, for 6 mo postpartum; infants in the LNS group received SQ-LNS formulated for infants from 6 to 18 mo of age (endline). The primary outcome was child length by 18 mo of age.
Results: At endline, data were available for 85% of 1228 infants enrolled; overall mean length and length-for-age z score (LAZ) were 79.3 cm and -0.83, respectively, and 12% of the children were stunted (LAZ <-2). In analysis based on the intended treatment, mean ± SD length and LAZ for the LNS group (79.7 ± 2.9 cm and -0.69 ± 1.01, respectively) were significantly greater than for the IFA (79.1 ± 2.9 cm and -0.87 ± 0.99) and MMN (79.1 ± 2.9 cm and -0.91 ± 1.01) groups (p = 0.006 and p = 0.009, respectively). Differences were also significant for weight and weight-for-age z score but not head or midupper arm circumference, and the prevalence of stunting in the LNS group was 8.9%, compared with 13.7% in the IFA group and 12.9% in the MMN group (p = 0.12). In analysis based on actual supplement provided at enrollment, stunting prevalences were 8.9% compared with 15.1% and 11.5%, respectively (p = 0.045).
Conclusion: Provision of SQ-LNSs to women from pregnancy to 6 mo postpartum and to their infants from 6 to 18 mo of age may increase the child’s attained length by age 18 mo in similar settings. This trial was registered at clinicaltrials.gov as NCT00970866.
2015-politi.pdf: “The effects of the generalized use of iodized salt on occupational patterns in Switzerland”, (2015-12-15; backlinks; similar):
I estimate the long-term impact of the first large-scale nutritional supplementation program, salt iodization, which took place in Switzerland in the 1920s and 1930s. Iodized salt improved the health environment in utero, and it eradicated mental retardation caused by insufficient iodine intake. By exploiting variation in the pre-existing prevalence of iodine deficiency, as well as differences in the timing of the intervention across Swiss cantons, I show that cohorts born in previously highly deficient areas after the introduction of iodized salt were more likely to enter top-tier occupations with higher cognitive demands. As a result, wages of these cohorts were higher, accounting for about 1.9% of annual median earnings, or 2% of Swiss GDP per capita in 1991.
[Keywords: Iodine deficiency, cognitive ability, occupational choice, human capital, productivity]
2015-niemesh.pdf: “Ironing Out Deficiencies: Evidence from the United States on the Economic Effects of Iron Deficiency”, (2015-09-01; ; backlinks; similar):
Iron deficiency reduces productive capacity in adults and impairs cognitive development in children. In 1943, the United States government required the fortification of bread with iron to reduce iron deficiency in the working-age population during World War II.
This nationwide fortification of grain products increased per capita consumption of iron by 16%. I find that areas with lower levels of iron consumption prior to the mandate experienced greater increases in income and school enrollment in the 1940s. A long-term followup suggests that adults in 1970 with more exposure to fortification during childhood earned higher wages.
2015-monahan.pdf: “Costs and benefits of iodine supplementation for pregnant women in a mildly to moderately iodine-deficient population: a modelling analysis”, (2015-08-10; ; backlinks; similar):
Background: Results from previous studies show that the cognitive ability of offspring might be irreversibly damaged as a result of their mother’s mild iodine deficiency during pregnancy. A reduced intelligence quotient (IQ) score has broad economic and societal cost implications because intelligence affects wellbeing, income, and education outcomes. Although pregnancy and lactation lead to increased iodine needs, no UK recommendations for iodine supplementation have been issued to pregnant women. We aimed to investigate the cost-effectiveness of iodine supplementation versus no supplementation for pregnant women in a mildly to moderately iodine-deficient population for which a population-based iodine supplementation programme—for example, universal salt iodisation—did not exist.
Methods: We systematically searched MEDLINE, Embase, EconLit, and NHS EED for economic studies that linked IQ and income published in all languages until Aug 21, 2014. We took clinical data relating to iodine deficiency in pregnant women and the effect on IQ in their children aged 8–9 years from primary research. A decision tree was developed to compare the treatment strategies of iodine supplementation in tablet form with no iodine supplementation for pregnant women in the UK. Analyses were done from a health service perspective (analysis 1; taking direct health service costs into account) and societal perspective (analysis 2; taking education costs and the value of an IQ point itself into account), and presented in terms of cost (in sterling, relevant to 2013) per IQ point gained in the offspring. We made data-supported assumptions to complete these analyses, but used a conservative approach that limited the benefits of iodine supplementation and overestimated its potential harms.
Findings: Our systematic search identified 1361 published articles, of which eight were assessed to calculate the monetary value of an IQ point. A discounted lifetime value of an additional IQ point based on earnings was estimated to be £3297 (study estimates range from £1319 to £11 967) for the offspring cohort. Iodine supplementation was cost saving from both a health service perspective (saving £199 per pregnant woman [sensitivity analysis range –£42 to £229]) and societal perspective (saving £4476 per pregnant woman [sensitivity analysis range £540 to £4495]), with a net gain of 1·22 IQ points in each analysis. Base case results were robust to sensitivity analyses.
Interpretation: Iodine supplementation for pregnant women in the UK is potentially cost saving. This finding also has implications for the 1·88 billion people in the 32 countries with iodine deficiency worldwide. Valuation of IQ points should consider non-earnings benefits—eg, health benefits associated with a higher IQ not germane to earnings.
2014-politi.pdf: “The Impact of Iodine Deficiency Eradication on Schooling: Evidence from the Introduction of Iodized Salt in Switzerland”, (2014-05-09; backlinks; similar):
I study the impact of salt iodization in Switzerland on graduation rates. The programme, which began in 1922 and continues to this day, was the first wide-reaching nutritional intervention ever to take place. Iodine deficiency in utero causes mental retardation, and correcting the deficiency is expected to increase the productivity of a population by increasing its cognitive ability. The exogenous increase in cognitive ability brought about by the iodization program is also useful in the context of disentangling the effects of innate ability and education on later-life outcomes. I identify the impact of iodization on graduation rates by exploiting pre-existing geographic variation in the prevalence of iodine deficiency, as well as spatial and temporal variation in the introduction of iodized salt across Swiss cantons. By looking at sharp, discontinuous increases in iodized salt circulation I show that the eradication of iodine deficiency in previously deficient areas statistically-significantly increased graduation rates from upper secondary and tertiary education. My results are robust to falsification tests and different measures of iodine deficiency.
[Keywords: Cognitive ability, education, human capital, productivity]
“Is Working Memory Training Effective? A Meta-Analytic Review”, (2013-02; ; backlinks; similar):
It has been suggested that working memory training programs are effective both as treatments for attention-deficit/hyperactivity disorder (ADHD) and other cognitive disorders in children and as a tool to improve cognitive ability and scholastic attainment in typically developing children and adults. However, effects across studies appear to be variable, and a systematic meta-analytic review was undertaken. To be included in the review, studies had to be randomized controlled trials or quasi-experiments without randomization, have a treatment, and have either a treated group or an untreated control group.
23 studies with 30 group comparisons met the criteria for inclusion. The studies included involved clinical samples and samples of typically developing children and adults. Meta-analyses indicated that the programs produced reliable short-term improvements in working memory skills. For verbal working memory, these near-transfer effects were not sustained at follow-up, whereas for visuospatial working memory, limited evidence suggested that such effects might be maintained. More importantly, there was no convincing evidence of the generalization of working memory training to other skills (nonverbal and verbal ability, inhibitory processes in attention, word decoding, and arithmetic).
The authors conclude that memory training programs appear to produce short-term, specific training effects that do not generalize. Possible limitations of the review (including age differences in the samples and the variety of different clinical conditions included) are noted. However, current findings cast doubt on both the clinical relevance of working memory training programs and their utility as methods of enhancing cognitive functioning in typically developing children and healthy adults.
[Keywords: working memory training, ADHD, attention, learning disabilities]
“The impact of iodine supplementation and bread fortification on urinary iodine concentrations in a mildly iodine deficient population of pregnant women in South Australia”, (2013; backlinks; similar):
Mild iodine deficiency during pregnancy can have statistically-significant effects on fetal development and future cognitive function. The purpose of this study was to characterise the iodine status of South Australian women during pregnancy and relate it to the use of iodine-containing multivitamins. The impact of fortification of bread with iodized salt was also assessed. Women (n = 196) were recruited prospectively at the beginning of pregnancy and urine collected at 12, 18, 30, 36 weeks gestation and 6 months postpartum. The use of a multivitamin supplement was recorded at each visit. Spot urinary iodine concentrations (UIC) were assessed. Median UICs were within the mildly deficient range in women not taking supplements (<90 μg/L). Among the women taking iodine-containing multivitamins UICs were within WHO recommendations (150–249 μg/L) for sufficiency and showed an increasing trend through gestation. The fortification of bread with iodized salt increased the median UIC from 68 μg/L to 84 μg/L (p = 0.011) which was still in the deficient range. Pregnant women in this region of Australia were unlikely to reach recommended iodine levels without an iodine supplement, even after the mandatory iodine supplementation of bread was instituted in October 2009.
Iodine: “Iodine and Adult IQ meta-analysis”, (2012-02-29; ; backlinks; similar):
Iodine improves IQ in fetuses; adults as well? A meta-analysis of relevant studies says no.
Iodization is one of the great success stories of public health intervention: iodizing salt costs pennies per ton, but as demonstrated in randomized & natural experiments, prevents goiters, cretinism, and can boost population IQs by a fraction of a standard deviation in the most iodine-deficient populations.
These experiments are typically done on pregnant women, and results suggest that the benefits of iodization diminish throughout the trimesters of a pregnancy. So does iodization benefit normal healthy adults, potentially even ones in relatively iodine-sufficient Western countries?
Compiling existing post-natal iodization studies which use cognitive tests, I find that—outliers aside—the benefit appears to be nearly zero, and so likely it does not help normal healthy adults, particularly in Western adults.
“Iodine intake in human nutrition: a systematic literature review”, (2012; backlinks; similar):
The present literature review is a part of the NNR5 project with the aim of reviewing and updating the scientific basis of the 4th edition of the Nordic Nutrition Recommendations (NNR) issued in 2004. The main objective of the review is to assess the influence of different intakes of iodine at different life stages (infants, children, adolescents, adults, elderly, and during pregnancy and lactation) in order to estimate the requirement for adequate growth, development, and maintenance of health.
The literature search resulted in 1,504 abstracts. Out of those, 168 papers were identified as potentially relevant. Full paper selection resulted in 40 papers that were quality assessed (A, B, or C). The grade of evidence was classified as convincing, probable, suggestive, and no conclusion.
We found suggestive evidence for improved maternal iodine status and thyroid function by iodine supplementation during pregnancy. Suggestive evidence was found for the relationship between improved thyroid function (used as an indicator of iodine status) during pregnancy and cognitive function in the offspring up to 18 months of age. Moderately to severely iodine-deficient children will probably benefit from iodine supplementation or improved iodine status in order to improve their cognitive function, while only one study showed improved cognitive function following iodine supplementation in children from a mildly iodine-deficient area (no conclusion).
No conclusions can be drawn related to other outcomes included in our review. There are no new data supporting changes in dietary reference values for children or adults. The rationale for increasing the dietary reference values for pregnant and lactating women in the NNR5 needs to be discussed in a broader perspective, taking iodine status of pregnant women in the Nordic countries into account.
Nootropics: “Nootropics”, (2010-01-02; ; backlinks; similar):
Notes on nootropics I tried, and my experiments
Bacopa is a supplement herb often used for memory or stress adaptation. Its chronic effects reportedly take many weeks to manifest, with no important acute effects. Out of curiosity, I bought 2 bottles of Bacognize Bacopa pills and ran a non-randomized non-blinded ABABA quasi-self-experiment from June 2014 to September 2015, measuring effects on my memory performance, sleep, and daily self-ratings of mood/productivity. Because of the very slow onset, small effective sample size, definite temporal trends probably unrelated to Bacopa, and noise in the variables, the results were as expected, ambiguous, and do not strongly support any correlation between Bacopa and memory/sleep/self-rating (+/-/- respectively).
“IQ in the Ramsey Model: A Naïve Calibration”, (2006; ; backlinks; similar):
I show that in a conventional Ramsey model, between one-fourth and one-half of the global income distribution can be explained by a single factor: The effect of large, persistent differences in national average IQ on the private marginal product of labor. Thus, differences in national average IQ may be a driving force behind global income inequality. These persistent differences in cognitive ability—which are well-supported in the psychology literature—are likely to be somewhat malleable through better health care, better education, and especially better nutrition in the world’s poorest countries. A simple calibration exercise in the spirit of Bils and Klenow (2000) and Castro (2005) is conducted. I show that an IQ-augmented Ramsey model can explain more than half of the empirical relationship between national average IQ and GDP per worker. I provide evidence that little of the IQ-productivity relationship is likely to be due to reverse causality.
2002-case.pdf: “Economic Status and Health in Childhood: The Origins of the Gradient”, (2002-12-01; backlinks; similar):
The well-known positive association between health and income in adulthood has antecedents in childhood. Not only is children’s health positively related to household income, but the relationship between household income and children’s health becomes more pronounced as children age. Part of the relationship can be explained by the arrival and impact of chronic conditions. Children from lower-income households with chronic conditions have worse health than do those from higher-income households. The adverse health effects of lower income accumulate over children’s lives. Part of the intergenerational transmission of socioeconomic status may work through the impact of parents’ income on children’s health.
1969-kevany.pdf: “Prophylaxis and Treatment of Endemic Goiter with Iodized Oil in Rural Ecuador and Peru”, (1969-12-01; backlinks; similar):
Endemic goiter continues to be a substantial health problem in many areas of the world. In some areas the disease is so severe that cretinism and other associated defects are found. In many areas, geographic, economic, and other factors prevent the use of iodized salt as a preventive measure.
A pilot program using iodized poppy seed oil has been instituted in two rural communities in Ecuador and three in Peru. Results after ~2 years indicate the feasibility and effectiveness of the programs. There has been a sharp reduction in the incidence of goiter. Cretinism has not yet appeared among the progeny of the population injected with iodized oil, but several instances have appeared in control groups. The use of iodized oil as a public health procedure for the prevention of endemic goiter and its associated defects is an acceptable measure in regions where salt-iodization programs cannot be presently undertaken.