MILAN, ITALY — Being overweight or obese starting in early adulthood was associated with increased aortic stiffness and decreased performance in a memory test at around age 60, in a new study[1].

Researchers investigated this in a 30-year follow-up of participants in the UK Medical Research Council's National Survey of Health and Development (NSHD)/1946 birth cohort study. The greatest negative effect on later memory was seen in the participants who became obese at the youngest age (in their late 30s), said Dr Stefano Masi (University College London, UK) presenting the findings here at the European Society of Hypertension's European Society of Hypertension (ESH) 2015 Scientific Sessions.

"The main message is [that] cumulative exposure to obesity since age 36 is associated with later memory dysfunction, and this impact seems to be independent of the acquisition of cardiovascular disease," Masi said, speaking with heartwire for Medscape and cochair Dr Zbigniew Gaciong (Warsaw Medical School, Poland) after his presentation. Encouragingly, the research suggested that dropping one body-mass-index (BMI) category and maintaining this weight loss might reverse these memory-dampening effects, he added.

Gaciong agreed that "the good news is that when you normalize your body weight, your cognitive function may improve." He suggested that this study shows that, similar to the impact of cigarette pack-years on health, the number of "obesity-years" has an impact on later memory.

"Our study confirms previous evidence suggesting that if you really control your body weight, you are able to make a difference for your cognition," Masi concurred. "It's an investment for the future."

Obesity, Aortic Pulse-Wave Velocity, and Memory

Obesity is a known risk factor for impaired cognitive function and is associated with increased aortic pulse-wave velocity and carotid intima-media thickness (IMT) (two subclinical markers of atherosclerosis that are themselves linked with an increased risk of cognitive decline), Masi explained. Moreover, pulse-wave velocity was recently associated with an increased rate of amyloid deposition in the brain.

The researchers sought to determine whether some of the cognitive decline associated with obesity is explained by an increased pulse-wave velocity or by carotid IMT.

Masi and colleagues analyzed data from 1233 participants in the 1946 birth cohort study who were 60 to 64 years old in the 2006–2010 span. The participants had complete data for BMI, aortic pulse-wave velocity, aortic calcification score, and carotid IMT, which was determined at age 36, 43, 53, and 60 to 64.

The participants also had results from a word-recall test at their last follow-up. For that memory test, they were given 15 words with 2 seconds to memorize each word, and then asked to write down as many words as they could remember in 1 minute; the test was repeated three times to obtain a total score.

The participants were divided into seven groups based on their BMIs:

Normal weight (for the whole study).

Became obese or overweight at age 36, 43, 53, or 60 to 64.

Became obese or overweight; then dropped and did not regain one BMI category.

Became obese or overweight; then dropped and regained one BMI category.

When they were age 60 to 64, as expected, overweight or obese participants had increased levels of markers of metabolic syndrome (blood pressure, lipids, HbA 1c ) and lower levels of leptin and adiponectin than their normal-weight peers. They also had worse results on the memory test (P<0.001) and higher carotid IMT (P<0.001), aortic pulse-wave velocity (P<0.002) and aortic calcium scores (P=0.012) than their normal-weight peers.

Higher BMI was associated with worse performance in the word-recall test, even after adjustment for sex, heart rate, education, and systolic blood pressure.

Similarly, higher pulse-wave velocity was associated with worse performance in this test. However, carotid IMT was not tied to results on this test.

The association of BMI with the memory-test results remained similar after adjustment for pulse-wave velocity, suggesting that these two factors have a separate impact on memory, Masi said.

Subjects who were overweight or obese at age 36 and remained in these weight categories during the follow-up had the worst performance on the word recall test.

However, in individuals who, at any point, dropped one BMI category, memory function and vascular phenotypes (carotid IMT, aortic pulse-wave velocity, and aortic calcification score) were similar to those of normal-weight subjects.

On the other hand, the beneficial effect of weight loss on memory function was lost if people regained weight. "If instead they dropped one category of BMI but regained weight, the score dropped down to the level of the people who had been always [overweight or] obese during follow-up," Masi said.

This might be explained by changes in insulin resistance, he speculated. "We know insulin resistance is a strong risk factor for Alzheimer's disease, and when you have a period of weight loss and regain, that is a strong risk factor for insulin resistance," he said. This could be explored in further research, he suggested.