summary: Associations 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 about the link between cognitive ability and BMI may be biased by shared family factors, rather than causation.
Well-reproduced associations between cognitive ability and body mass index (BMI) may largely reflect confounding due to other factors related to family background, according to a new study published April 13.y In Open Access Journal 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 rise. Current studies have found links between cognitive ability and obesity, with lower cognitive ability in childhood or adolescence associated with a higher BMI or a higher rate of obesity in late adulthood.
In the new study, the researchers used data on 12,250 siblings from 5,602 families followed from adolescence to age 62 as part of four separate studies of youth cohorts in the United States. By comparing the relationship between cognitive ability and BMI within families, the team could take into account non-observable factors related to family background.
When comparing unrelated individuals in the data set, the researchers found that going from 25y up to 75y The percentage of adolescent cognitive ability was associated with an estimated 0.61 kg/m2 A decrease in body mass index (95% CI -0.90 to -0.33) when adjusted for family socioeconomic status.
However, when comparing siblings, going from 25y up to 75y The percentage of adolescent cognitive ability was associated with only 0.06 kg/m2 Decrease in body mass index (95% CI -0.35 to 0.23).
The authors say, “The results indicate that current findings on the association between cognitive ability and BMI are biased by shared familial factors.” “Because associations between cognitive ability and other health outcomes were found using similar observational research designs, sibling data may be useful for assessing potential bias for these health outcomes as well.”
Wright adds, “Does higher cognitive ability (intelligence) help one avoid gaining too much weight? A lot of studies have found an association between the two, but our study suggests that these associations may not be causal in nature.”
About this obesity and cognitive research news
author: Claire Turner
communication: Claire Turner – Plus
picture: The image is in the public domain
Original search: open access.
“Association between cognitive ability and body mass index: a sibling comparison analysis in four longitudinal studies” by Liam Wright et al. PLOS medicine
The relationship between cognitive ability and body mass index: a sibling comparison analysis in four longitudinal studies
Body mass index (BMI) and obesity rates have increased sharply since the 1980s. While several epidemiological studies have found that higher cognitive ability in adolescents is associated with lower BMI in adults, residual and unobserved confusion due to family background may explain these associations. We used a sibling design to test this association in accounting for common confounding factors within families.
Methods and results
We used data from four public cohort studies of youth in the United States: the National Longitudinal Study of Youth 1979 (NLSY-79), NLSY-79 Children and Youth, NLSY 1997 (NLSY-97), and the Wisconsin Longitudinal Study (WLS); A total of 12,250 siblings from 5,602 households followed from adolescence to age 62. We used random effects within (REWB) and residual quantitative regression (RQR) models to compare intra- and within-family estimates of the association between adolescent cognitive ability and adult BMI (20 to 64). year).
In the REWB paradigms, the transition from the 25th to 75th percentile of adolescent cognitive ability was associated with -0.95 kg/m.2 (95% CI = −1.21, −0.69) Low BMI among families. Adjustment for household socioeconomic status reduced the association to −0.61 kg/m2 (0.90, 0.33). However, within families, the correlation was only 0.06 kg/m2 (0.35, 0.23).
This pattern of results has been found across multiple parameters, including analyzes conducted in separate cohorts, models examining age differences in association, and in RQR models examining association across BMI distribution. Limitations include the possibility that within-family estimates may be biased by exposure measurement error, confounding by non-shared factors, and carry-over effects.
The association between higher adolescent cognitive ability and lower adult BMI was significantly smaller in the intra-household analysis than in the intra-household analysis. Well-reproduced associations between cognitive ability and subsequent BMI may largely reflect confounding from family background factors.