Nutritional supplementation in early childhood, schooling, and intellectual functioning in adulthood: a prospective study in Guatemala

Abstract

Objective: To estimate the association of improved nutrition in early life with adult intellectual functioning, controlling for years of schooling.

Design: Prospective cohort study.

Setting: Four villages in Guatemala, as well as locations within Guatemala to which cohort members migrated.

Participants: Individuals who had participated as children in a nutrition supplementation intervention trial from March 1, 1969, through February 28, 1977 (N = 2392). From May 1, 2002, through April 30, 2004, adequate information for analysis was obtained from 1448 of 2118 individuals (68.4%) not known to have died.

Interventions: Individuals exposed to atole (a protein-rich enhanced nutrition supplement) at birth through age 24 months were compared with those exposed to the supplement at other ages or to fresco, a sugar-sweetened beverage. We measured years of schooling by interview.

Main outcome measures: Scores on the Serie Interamericana (InterAmerican Series) tests of reading comprehension and the Raven Progressive Matrices, obtained from May 1, 2002, through April 30, 2004.

Results: In models controlling for years of schooling and other predictors of intellectual functioning, exposure to atole at birth to age 24 months was associated with an increase of 3.46 points (95% confidence interval, -1.26 to 8.18) and 1.74 points (95% confidence interval, 0.53-2.95) on the InterAmerican Series and Raven Progressive Matrices tests, respectively. There was no statistical interaction between exposure to atole at birth to age 24 months and years of schooling on either outcome (P = .24 and P = .60, respectively).

Conclusion: Improved early-life nutrition is associated with increased intellectual functioning in adulthood after taking into account the effect of schooling.

Figure 1

Performance on the Serie Interamericana (InterAmerican Reading Series) reading comprehension tests among participants in the 2002–2004 follow-up survey to a longitudinal study in Guatemala conducted from 1969–1977, by exposure to atole at birth to age 24 months and schooling (ie, highest grade attained). Data are least-squares means and 95% confidence intervals and are adjusted for sex; year of birth; socioeconomic status in 1967 or 1975; maternal and paternal years of schooling, maternal and paternal age at respondent’s birth (years, log transformed); distance from house to feeding center (2 dummies); student to teacher ratio when the respondent was aged 7 and 12 years; school construction materials when the respondent was aged 7 and 12 years (permanent materials vs other); and clustering of subjects within family and families within village. Data for grades 7 through 9 and for grades 10 and higher are pooled because of small sample sizes and are presented at the group median (grades 8 and 12, respectively).

Figure 2

Performance on the Raven Progressive Matrices among participants in the 2002–2004 follow-up survey to a longitudinal study in Guatemala conducted from 1969 through 1977, by exposure to atole at birth to age 24 months and schooling. Data are least-squares means and 95% confidence intervals, and are adjusted for sex; year of birth; socioeconomic status in 1967 or 1975; maternal and paternal years of schooling; maternal and paternal age at respondent’s birth (years, log transformed); distance from house to feeding center (2 dummies); student to teacher ratio when the respondent was aged 7 and 12 years; school construction materials when the respondent was aged 7 and 12 years (permanent materials vs other); and clustering of subjects within family and families within village. Data for grades 7 through 9 and for grades 10 and higher are pooled because of small sample sizes and are presented at the group median (grades 8 and 12, respectively).