Adiposity in the older population and the risk of dementia: The Rotterdam Study

I'm not sure women want to keep this fat as a preventative to dementia.

Gynoid fat is the body fat that forms around the hips, breasts and thighs.^[1] Gynoid fat in females is used to provide nourishment for offspring, and is often referred to as 'reproductive fat'. 

Adiposity in the older population and the risk of dementia: The Rotterdam Study

Sanne S. Mooldijk, Tosca O. E. de Crom, M. Kamran Ikram, M. Arfan Ikram, Trudy Voortman

First published: 29 November 2022

https://doi.org/10.1002/alz.12888

Sanne S. Mooldijk and Tosca O. E. de Crom contributed equally to this study.

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Abstract

Introduction

We determined associations of total and regional adiposity with incident dementia among older adults.

Methods

Within the population-based Rotterdam Study, adiposity was measured as total, android, and gynoid fat mass using dual-energy X-ray absorptiometry in 3408 men and 4563 women, every 3 to 6 years between 2002 and 2016. Incident dementia was recorded until 2020.

Results

Higher adiposity measures were associated with a decreased risk of dementia in both sexes. After excluding the first 5 years of follow-up, only the association of gynoid fat among women remained significant (hazard ratio 0.85 [95% confidence interval 0.75–0.97] per standard deviation increase). No major differences in trajectories of adiposity measures were observed between dementia cases and dementia-free controls.

Discussion

Higher total and regional fat mass related to a decreased risk of dementia. These results may be explained by reverse causality, although a protective effect of adiposity cannot be excluded.

Highlights

• Total and regional adiposity were assessed using dual-energy X-ray absorptiometry scans in 7971 older adults.
• All adiposity measures were associated with a decreased risk of dementia.
• The results suggest a beneficial effect of gynoid fat on the risk of dementia in women.
• Reverse causation and competing risk may explain these inverse associations.

1 INTRODUCTION

Obesity and dementia are both substantial public health problems worldwide.^{1, 2} Obesity during mid-life is a well-established risk factor for dementia later in life,^3-5 which may be explained by excessive adipose tissue.⁶ Especially visceral fat, located around the abdominal organs, is thought to underlie this via metabolic dysfunction, for example, hypertension, insulin resistance, and dyslipidemia.^{7, 8}

Although visceral fat at older age likely affects the brain through similar metabolic dysfunctions, obesity at older age has consistently been linked to a decreased risk of dementia.^{4, 9-12} This may be explained by reverse causality, that is, weight loss caused by preclinical dementia symptoms,^13-15 but biological mechanisms for a protective effect of subcutaneous adipose tissue in the gynoid (i.e., hips) region have also been suggested.^{16, 17} These different health effects of adipose tissue deposits highlight the need to differentiate between total and regional adipose tissue, particularly in older adults, as adipose tissue increases and the distribution changes during the aging process.¹⁸

Yet, existing literature on the link between obesity and the risk of dementia mostly used body mass index (BMI) or waist circumference as marker of obesity, which do not necessarily reflect the amount and location of adipose tissue.^19-22 Alternatively, total and regional fat mass can be obtained using dual-energy X-ray absorptiometry (DXA), which allows the quantification of fat in the android (i.e., abdominal) and gynoid region.²¹ Android fat accumulation is typically seen in men and includes visceral fat, while gynoid fat is typically seen in women and comprises of subcutaneous fat.

To improve the understanding of the effects of adiposity on the risk of dementia among older adults, we examined associations of measures of adiposity derived from DXA scans, namely total body mass, total fat mass, android fat mass, and gynoid fat mass, with the risk of dementia in men and women separately. In addition, to understand the potential role of reverse causality in this association, we determined trajectories of adiposity measures before dementia diagnosis and compared those to trajectories of dementia-free controls.

 

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