Abstract
Background: It is known that obesity [measured with body mass index (BMI)] relates to brain structure and markers of cerebral small vessel disease (CSVD). However, BMI may not adequately represent body composition. Furthermore, whether those cross-sectional associations hold longitudinally remains uncertain.Methods: Three thousand six hundred and fourty-eight participants underwent baseline (2006–2014) dual-energy X-ray absorptiometry (DXA)-scan to obtain detailed measures of body composition and a magnetic resonance imaging (MRI) scan to assess brain structure. One thousand eight hundred and fourty-four participants underwent a second MRI-scan at follow-up (2010–2017; median follow-up: 5.5 years). To assess cross-sectional and longitudinal associations (measures of change have been calculated) between body composition [BMI, fat mass index (FMI), fat-free mass index (FFMI)], and brain tissue volume (gray matter, white matter, hippocampus), white matter microstructure [fractional anisotropy (FA), mean diffusivity (MD)], and CSVD markers (white matter hyperintensity volume, lacunes, microbleeds) we used multivariable linear and logistic regression models.Results: A higher BMI and FMI were cross-sectionally associated with smaller white matter volumes (difference in Z-score per SD higher BMI: −0.064 [95% CI: −0.094, −0.035]) and FMI: −0.067 [95% CI: −0.099, −0.034], higher FA and MD. A higher FFMI was associated larger gray matter volume (difference: 0.060 [95% CI: 0.018, 0.101]). There was no statistically significant or clinically relevant association between body composition and brain changes.Conclusions: Body composition, distinguishing between fat mass and fat-free mass, does not directly influence changes in brain tissue volume, white matter integrity and markers of CSVD. Cross-sectional associations between body composition and brain tissue volume likely reflect cumulative risk or shared etiology.
Highlights
The increasing prevalence of obesity is accompanied by numerous adverse health effects, including cognitive decline and dementia [1, 2]
Researchers found that fat mass index (FMI) was independently and positively associated with the presence of metabolic syndrome regardless of body mass index (BMI) and concluded that FMI is a better approximation of body composition [8]
We studied the association of body composition, divided into body mass, fat mass, and fat-free mass, with brain tissue volume, white matter integrity and markers of cerebral small vessel disease (CSVD) (white matter lesion hyperintensities (WMH), lacunes, and microbleeds) to evaluate whether fat mass and fat-free mass is a better approximation of body composition
Summary
The increasing prevalence of obesity is accompanied by numerous adverse health effects, including cognitive decline and dementia [1, 2]. It has been found that obesity is associated with focal brain pathology in the form of cerebral small vessel disease (CSVD) [6]. An important limitation of previous studies is that obesity is generally assessed by body mass index (BMI) [2]. Researchers found that fat mass index (FMI) was independently and positively associated with the presence of metabolic syndrome regardless of BMI and concluded that FMI is a better approximation of body composition [8]. It is known that obesity [measured with body mass index (BMI)] relates to brain structure and markers of cerebral small vessel disease (CSVD). BMI may not adequately represent body composition Whether those cross-sectional associations hold longitudinally remains uncertain
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