Link Between Cognitive Ability and Body Mass Index May Be Biased

New study shows shared family factors may explain previous findings

By Lori Solomon HealthDay Reporter

FRIDAY, April 14, 2023 (HealthDay News) — Existing findings on the link between cognitive ability and body mass index (BMI) may be biased by shared family factors, according to a study published online April 13 in PLOS Medicine.

Liam Wright, Ph.D., from University College London, and colleagues used data from a total of 12,250 siblings from 5,602 households followed from adolescence up to age 62 years to assess the relationship between cognitive ability and BMI.

The researchers found that moving from the 25th to 75th percentile of adolescent cognitive ability was associated with âˆ’0.95 kg/mÂ² (95 percent confidence interval, âˆ’1.21 to âˆ’0.69) lower BMI between families, but this association was reduced to âˆ’0.61 kg/mÂ² (95 percent confidence interval, âˆ’0.90 to âˆ’0.33) when adjusting for family socioeconomic position. Within families, this association was just âˆ’0.06 kg/mÂ² (95 percent confidence interval, âˆ’0.35 to 0.23). Results showed a consistent pattern across cohorts, when examining age differences, and across the distribution of BMI.

“The results suggest that existing findings on the link between cognitive ability and BMI are biased by shared family factors,” the authors write. “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.”