The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies
<h4>Background</h4> Body mass index (BMI) and obesity rates have increased sharply since the 1980s. While multiple epidemiologic studies have found that higher adolescent cognitive ability is associated with lower adult BMI, residual and unobserved confounding due to family background ma...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Public Library of Science (PLoS)
2023-04-01
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| Series: | PLoS Medicine |
| Online Access: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10101525/?tool=EBI |
| _version_ | 1797846138004439040 |
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| author | Liam Wright Neil M. Davies David Bann |
| author_facet | Liam Wright Neil M. Davies David Bann |
| author_sort | Liam Wright |
| collection | DOAJ |
| description | <h4>Background</h4> Body mass index (BMI) and obesity rates have increased sharply since the 1980s. While multiple epidemiologic studies have found that higher adolescent cognitive ability is associated with lower adult BMI, residual and unobserved confounding due to family background may explain these associations. We used a sibling design to test this association accounting for confounding factors shared within households. <h4>Methods and findings</h4> We used data from four United States general youth population cohort studies: the National Longitudinal Study of Youth 1979 (NLSY-79), the NLSY-79 Children and Young Adult, the NLSY 1997 (NLSY-97), and the Wisconsin Longitudinal Study (WLS); a total of 12,250 siblings from 5,602 households followed from adolescence up to age 62. We used random effects within-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 REWB models, moving from the 25th to 75th percentile of adolescent cognitive ability was associated with −0.95 kg/m2 (95% CI = −1.21, −0.69) lower BMI between families. Adjusting for family socioeconomic position reduced the association to −0.61 kg/m2 (−0.90, −0.33). However, within families, the association was just −0.06 kg/m2 (−0.35, 0.23). This pattern of results was found across multiple specifications, including analyses conducted in separate cohorts, models examining age-differences in association, and in RQR models examining the association across the distribution of BMI. Limitations include the possibility that within-family estimates are biased due to measurement error of the exposure, confounding via non-shared factors, and carryover effects. <h4>Conclusions</h4> The association between high adolescent cognitive ability and low adult BMI was substantially smaller in within-family compared with between-family analysis. The well-replicated associations between cognitive ability and subsequent BMI may largely reflect confounding by family background factors. Liam Wright and colleagues investigate the association between adolescent cognitive ability and adult body mass index using a sibling design that accounts for confounding factors within households. Author summary <h4>Why was this study done?</h4> Obesity is a major contributor to global disease burden, and its prevalence is expected to continue to rise. While obesity rates have increased, body mass has not increased uniformly across the population, suggesting a role of individual characteristics in determining obesity; one such characteristic is cognitive ability. Existing studies reporting links between cognitive ability and obesity have made adjustment for observed confounders only; they may thus be biased by residual or unobserved confounding. <h4>What did the researchers do and find?</h4> We used data from four cohorts of siblings (n = 12,250) to examine the association between childhood cognitive ability and adult body mass index (BMI) within families. This approach can account for unobserved factors that may bias an association between cognitive ability and BMI that are shared between siblings, such as family socioeconomic position. When looking within families, we found little evidence of an association between cognitive ability and (lower) BMI, contrary to results of conventional analysis and existing studies in this literature: Moving from the 25th to 75th centile of cognitive ability was associated with a −0.06 kg/m2 (−0.35, 0.23) difference in BMI. <h4>What do these findings mean?</h4> The results suggest that existing findings on the link between cognitive ability and BMI are biased by shared family factors. Given that 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 these health outcomes, too. |
| first_indexed | 2024-04-09T17:51:09Z |
| format | Article |
| id | doaj.art-22a05eb6c29a4113b0a717610960fd5e |
| institution | Directory Open Access Journal |
| issn | 1549-1277 1549-1676 |
| language | English |
| last_indexed | 2024-04-09T17:51:09Z |
| publishDate | 2023-04-01 |
| publisher | Public Library of Science (PLoS) |
| record_format | Article |
| series | PLoS Medicine |
| spelling | doaj.art-22a05eb6c29a4113b0a717610960fd5e2023-04-16T05:31:18ZengPublic Library of Science (PLoS)PLoS Medicine1549-12771549-16762023-04-01204The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studiesLiam WrightNeil M. DaviesDavid Bann<h4>Background</h4> Body mass index (BMI) and obesity rates have increased sharply since the 1980s. While multiple epidemiologic studies have found that higher adolescent cognitive ability is associated with lower adult BMI, residual and unobserved confounding due to family background may explain these associations. We used a sibling design to test this association accounting for confounding factors shared within households. <h4>Methods and findings</h4> We used data from four United States general youth population cohort studies: the National Longitudinal Study of Youth 1979 (NLSY-79), the NLSY-79 Children and Young Adult, the NLSY 1997 (NLSY-97), and the Wisconsin Longitudinal Study (WLS); a total of 12,250 siblings from 5,602 households followed from adolescence up to age 62. We used random effects within-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 REWB models, moving from the 25th to 75th percentile of adolescent cognitive ability was associated with −0.95 kg/m2 (95% CI = −1.21, −0.69) lower BMI between families. Adjusting for family socioeconomic position reduced the association to −0.61 kg/m2 (−0.90, −0.33). However, within families, the association was just −0.06 kg/m2 (−0.35, 0.23). This pattern of results was found across multiple specifications, including analyses conducted in separate cohorts, models examining age-differences in association, and in RQR models examining the association across the distribution of BMI. Limitations include the possibility that within-family estimates are biased due to measurement error of the exposure, confounding via non-shared factors, and carryover effects. <h4>Conclusions</h4> The association between high adolescent cognitive ability and low adult BMI was substantially smaller in within-family compared with between-family analysis. The well-replicated associations between cognitive ability and subsequent BMI may largely reflect confounding by family background factors. Liam Wright and colleagues investigate the association between adolescent cognitive ability and adult body mass index using a sibling design that accounts for confounding factors within households. Author summary <h4>Why was this study done?</h4> Obesity is a major contributor to global disease burden, and its prevalence is expected to continue to rise. While obesity rates have increased, body mass has not increased uniformly across the population, suggesting a role of individual characteristics in determining obesity; one such characteristic is cognitive ability. Existing studies reporting links between cognitive ability and obesity have made adjustment for observed confounders only; they may thus be biased by residual or unobserved confounding. <h4>What did the researchers do and find?</h4> We used data from four cohorts of siblings (n = 12,250) to examine the association between childhood cognitive ability and adult body mass index (BMI) within families. This approach can account for unobserved factors that may bias an association between cognitive ability and BMI that are shared between siblings, such as family socioeconomic position. When looking within families, we found little evidence of an association between cognitive ability and (lower) BMI, contrary to results of conventional analysis and existing studies in this literature: Moving from the 25th to 75th centile of cognitive ability was associated with a −0.06 kg/m2 (−0.35, 0.23) difference in BMI. <h4>What do these findings mean?</h4> The results suggest that existing findings on the link between cognitive ability and BMI are biased by shared family factors. Given that 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 these health outcomes, too.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10101525/?tool=EBI |
| spellingShingle | Liam Wright Neil M. Davies David Bann The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies PLoS Medicine |
| title | The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies |
| title_full | The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies |
| title_fullStr | The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies |
| title_full_unstemmed | The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies |
| title_short | The association between cognitive ability and body mass index: A sibling-comparison analysis in four longitudinal studies |
| title_sort | association between cognitive ability and body mass index a sibling comparison analysis in four longitudinal studies |
| url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10101525/?tool=EBI |
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