Increased body mass index (BMI) and metabolic abnormality were significantly associated with cognitive decline, researchers found.
Compared with a group of normal-weight and metabolically healthy people, those who were overweight, obese, or had a metabolic abnormality were significantly more likely to have impaired cognitive function (P<0.001), according to Archana Singh-Manoux, PhD, of the Hôpital Paul Brousse in Villejuif, France, and colleagues.
And those who were both obese and had a metabolic abnormality were significantly more likely to have a quicker rate of cognitive decline than either metabolically healthy obese patients or those who were normal weight or overweight with or without metabolic abnormality (P=0.03), they reported online in the journal Neurology.
The 10-year longitudinal study measured the association of BMI and metabolic status with cognitive function and decline in 6,401 British civil servants, ages 39 to 63 years at baseline, beginning in the years 1991 to 1993.
Participants submitted their BMI and metabolic status at baseline and were categorized as normal weight, overweight, or obese, and metabolically abnormal or normal.
Metabolic abnormality was defined as having two or more markers of metabolic abnormality, including:
- Use of lipid-lowering, antihypertensive, or diabetes drugs
- Triglycerides ≥1.69 mmol/L
- Systolic blood pressure ≥130 mm Hg
- Diastolic blood pressure ≥85 mm Hg
- Glucose ≥5.6 mmol/L
- High-density lipoprotein cholesterol <1.04 mmol/L in men or <1.29 mmol/L in women
Participants were given four cognitive tests on memory, reasoning, semantic, and phonemic fluency over a 10-year follow-up in 5-year intervals from 1997 to 1999, 2002 to 2004, and 2007 to 2009.
In the study, 52.7% of participants were normal weight, 38.2% were overweight, and 9.1% were obese. Of the total participants, 31% were considered metabolically abnormal, while 60.1% of obese patients were considered metabolically abnormal.
When compared with patients with normal weight and normal metabolism, increased BMI and/or metabolic abnormality were significantly associated with global scores in decreased cognitive function, including:
- Overweight, metabolically normal: z=-0.08 (95% CI -0.14 to -0.02)
- Obese, metabolically normal: z=-0.16 (95% CI -0.28 to -0.04)
- Normal weight, metabolically abnormal: z=-0.17 (95% CI -0.25 to -0.09)
- Overweight, metabolically abnormal: z=-0.17 (95% CI -0.23 to -0.10)
- Obese, metabolically abnormal: z=-0.14 (95% CI -0.24 to -0.04)
Differences in cognitive decline in participants with normal and overweight status and in participants with and without metabolic abnormality were significant (P<0.001 and P=0.02, respectively). There was no significant difference in cognitive decline between the obese groups.
When measured for 10-year cognitive decline, there was a significant trend for faster decline among obese participants with metabolic abnormality compared with overweight and normal-weight patients who were metabolically abnormal (P=0.03). Comparisons between other groups at follow-up failed to reach significance.
The authors concluded that “lower BMI was associated with better cognition at baseline and similar cognitive decline as a function of BMI, suggesting that baseline differences were maintained but did not increase over time.”
They also noted that an “adverse metabolic profile” was more highly associated with poor cognitive function in normal and overweight groups than any other.
The researchers said possible mechanisms of action in the relationship between obesity and adverse cognitive outcomes include vascular pathologies, as well as secretion of adipose tissue, leptin, and adiponectin, “which affect the aging brain.”
Singh-Manoux and colleagues noted the study was limited by a sample of office-based civil servants who were not wholly representative of the British population.
The study was funded by the National Institutes of Health, the Academy of Finland, the BUPA Foundation, U.K., and the Medical Research Council, U.K.
Singh-Manoux received support from the NIH and the British MRC. One co-author received support from the NIH, the British MRC, and the Academy of Finland.
From the American Heart Association:
Mortality, Health Outcomes, and Body Mass Index in the Overweight Range
By Cole Petrochko, Associate Staff Writer, MedPage Today
Published: August 21, 2012
Reviewed by Dori F. Zaleznik, MD; Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, BSN, RN, Nurse Planner
© 2012 MedPage Today, LLC.