What is already known about this subject
- Obesity is associated with metabolic disease and impaired cognitive function in adults.
- Low birth weight is known to be associated with adult metabolic disease and low intellectual performance.
Overweight and obesity are risk factors for cardiovascular disease. There is also an association between body mass index (BMI) and cognitive ability. Since low birth weight is associated with adult metabolic disease, particularly in obese subjects, the question emerges whether obesity has an additional negative effect on cognitive function in subjects with low birth weight.
The aim was to analyse whether overweight or obesity influence intellectual performance in young adults with particular focus on those with a low birth weight.
Data were collected from the Swedish Medical Birth Register on 620 834 males born between 1973 and 1988 and matched to results on intellectual performance and BMI at conscription.
The risk for low intellectual performance was higher for those with high BMI compared to those with normal. The highest risk was found among subjects with low birth weight and overweight or obesity in young adulthood (odds ratios, 1.98 [1.73-2.22] and 2.59 [2.00–3.34], respectively). However, subjects with further high birth weight and a high BMI at conscription had no further increased risk.
Overweight and obesity are associated with an increased risk of subnormal intellectual performance in young adult males. Subjects with low birth weight and adolescent overweight/obesity are at particular risk of subnormal performance. A high birth weight increases the risk for obesity, but a high adult BMI does not further increase the risk for subnormal performance.