Summary: Correlations between cognitive ability and body mass index (BMI) may largely reflect confounding by other factors related to family background. The study suggests that previous findings on the link between cognitive ability and BMI may be biased by shared family factors, rather than causation.
Source: PLOS
The well-replicated associations between cognitive ability and body mass index (BMI) may largely reflect confounding by other factors related to family background, according to a new study published in April. 13th in open access journals PLoS Medicine by Liam Wright of University College London, UK, and colleagues.
Obesity is a major contributor to the global burden of disease and its prevalence is expected to continue to increase. Current studies have found links between cognitive ability and obesity, with lower cognitive ability in childhood or adolescence being associated with a higher BMI or a higher rate of obesity in old age.
In the new study, researchers used data on 12,250 siblings from 5,602 households who were followed from adolescence to age 62 as part of four separate population-based cohort studies of youth in the United States. united states By comparing the association between cognitive ability and BMI within families, the team could account for unobserved factors related to family background.
When comparing unrelated individuals in the dataset, the researchers found that the transition from 25th up to 75th Adolescent mental capacity percentage is associated with an estimated 0.61 kg/m2 decrease in BMI (95% CI -0.90 to -0.33) when adjusted for family socioeconomic position.
When comparing siblings, however, move from 25th up to 75th Adolescent mental ability percentage is only associated with a 0.06 kg/m2 decrease in BMI (95% CI -0.35 to 0.23).
“The results suggest that existing findings on the link between cognitive ability and BMI are biased by shared family factors,” the authors said. “Because associations between cognitive ability and other health outcomes have been found using similar observational research designs, sibling data may be useful for assessing potential bias for health outcomes as well.”
Wright added, “Does higher cognitive ability (intelligence) help prevent weight gain? Many studies have found a link between the two, but our study suggests that these links may not be causal in nature.
This news is about obesity and cognition research
Author: Claire Turner
Source: PLOS
Contact: Claire Turner – PLOS
Image: The image is in the public domain
Original Research: Open access.
“The relationship between cognitive ability and body mass index: A comparative analysis of siblings in four longitudinal studies” by Liam Wright et al. PLoS Medicine
Abstract
The relationship between cognitive ability and body mass index: A comparative analysis of siblings in four longitudinal studies
Background
Body mass index (BMI) and obesity rates have increased dramatically since the 1980s. While many epidemiologic studies have found that higher adolescent cognitive ability is associated with lower adult BMI, residual and unobserved confounding by family background may explain these associations. this. We used a sibling design to test this association taking into account confounding factors shared within households.
Methods and findings
We used data from four general population cohort studies of youth in the United States: the National Longitudinal Study of Youth 1979 (NLSY-79), the NLSY-79 Children and Young Adults, the NLSY 1997 (NLSY- 97), and the Wisconsin Longitudinal Study (WLS); a total of 12,250 siblings from 5,602 households were followed from youth to age 62. We used random effects between (REWB) and residualized quantile regression (RQR) models to compare between- and within-family estimates of the association between adolescent cognitive ability. and adult BMI (20 to 64 years).
In the REWB models, moving from the 25th to the 75th percentile of youth cognitive ability was associated with −0.95 kg/m2 (95% CI = −1.21, −0.69) lower BMI between families. Adjustment for family socioeconomic position reduced the association to −0.61 kg/m2 (−0.90, −0.33). However, within families, the association was −0.06 kg/m2 (−0.35, 0.23).
This pattern of results was found in several specifications, including analyzes conducted in separate cohorts, models examining age differences in association, and in RQR models examining association across BMI distributions. Limitations include the possibility that within-family estimates are biased due to exposure measurement error, confounding by nonshared factors, and carryover effects.
Conclusions
The association between high adolescent cognitive ability and low adult BMI was smaller in the within-family than in the between-family analysis. The well-replicated associations between cognitive ability and subsequent BMI may largely reflect confounding factors of family background.
