A study added to the evidence that the menopausal transition is a critical time for women and their doctors to focus on heart health, which protects their brain health.

Findings of the study published in the journal Alzheimer's & Dementia. "It is shocking to know that two-thirds of Americans with Alzheimer's disease are women," said Meiyuzhen (Chimey) Qi, first author and PhD candidate in epidemiology at Pitt Public Health.

"The most common modifiable risk factor for dementia is cardiovascular disease, and, interestingly, a woman's risk for cardiovascular disease increases after menopause. So the next logical step was to see if there was a link between cardiovascular risk factors related to the menopause transition such as the type of cardiovascular fat a woman has and her cognitive function later in life," Qi said.

The scientists went to the long-running Study of Women's Health Across the Nation (SWAN) and its supplementary study, SWAN Cardiovascular Fat, to investigate the idea.

SWAN observed a varied group of women in their forties as they went through the menopausal transition. 531 individuals, with an average age of 51, had scans to learn about the fat around their hearts and veins. They were then monitored for 16 years, with several cognitive tests administered along the way.

Cardiovascular fat is classified into three types: epicardial adipose tissue (EAT), paracardial adipose tissue (PAT), and thoracic perivascular adipose tissue (PVAT), which surrounds the longest portion of the body's largest artery leading away from the heart.

EAT and PAT are often poorer quality "white" fats that the body retains, but thoracic PVAT is a better quality "brown" fat that the body easily transforms to energy. The density of fat in the scans was employed as a measure of fat quality by the researchers.

In this study, the researchers assessed how the quantity and quality of cardiovascular fat during midlife are related to cognitive function as women age.

Quantity was measured as the volume of fat, whereas quality was determined based on the density of fat. A greater volume of thoracic PVAT during midlife was related to stronger long-term memory later in life, while a higher density of thoracic PVAT -- likely reflecting lower quality white fat -- was linked to worsening working memory.

"This is an association. We cannot say with any certainty that higher or lower quality cardiovascular fat causes Alzheimer's disease -- but it is a tantalising clue that makes sense," said senior author Dr Samar El Khoudary, professor of epidemiology at Pitt Public Health.

"Of the different types of heart fat, PVAT is located the closest to brain circulation and brown fat is linked to better whole-body metabolism and lower markers for inflammation."

During the menopause transition, women usually experience vascular or fat tissue inflammation, which may manifest as thoracic PVAT with higher density, meaning it is of lower quality.

Previous studies have found that vascular inflammation promotes plaque formation, and inflamed fat tissue has the abnormal secretion of cell signalling molecules, which predispose people to cognitive decline.

The SWAN Cardiovascular Fat ancillary study was limited, so the researchers stressed that more studies will be needed to see if the findings extend to women of other races and ethnicities or to men.

And further research is needed to determine if the type of cardiovascular fat actually causes cognitive decline or if efforts to modify the quality of cardiovascular fat -- such as taking anti-inflammatory medications -- can stave off dementia.

"That said, I believe our study is more evidence that taking care of your heart helps take care of your brain and that menopause is a particularly sensitive time for the heart as well as brain health," El Khoudary said.

"So staying active and regularly doing cardiovascular exercises that get your heart pumping, as well as eating a healthy diet and keeping up with doctor's appointments, are all especially important at midlife. Protecting your heart during the menopausal transition may be protecting your brain in the future."