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Additional file 1.

Additional file 1. Modules included in the BHIS 2018.

Aging is associated with alterations in the brain including structural and metabolic changes. Previous research has focused on neurometabolite level differences associated to age in a variety of brain regions, but the relationship among metabolites across the brain has been much less studied. Investigating these relationships can reveal underlying neurometabolic processes, their interdependency, and their progress throughout the lifespan. Using 1 H-MRS, we investigated the relationship among metabolite concentrations of N-acetylaspartate (NAA), creatine (Cr), choline (Cho), myo-Inositol (mIns) and glutamate-glutamine complex (Glx) in seven voxel locations, i.e., bilateral sensorimotor cortex, bilateral striatum, pre-supplementary motor area, right inferior frontal gyrus and occipital cortex. These measurements were performed on 59 human participants divided in two age groups: young adults (YA: 23.2 ± 4.3; 18-34 years) and older adults (OA: 67.5 ± 3.9; 61-74 years). Our results showed age-related differences in NAA, Cho, and mIns across brain regions, suggesting the presence of neurodegeneration and altered gliosis. Moreover, associative patterns among NAA, Cho and Cr were observed across the selected brain regions, which differed between young and older adults. Whereas most of metabolite concentrations were inhomogeneous across different brain regions, Cho levels were shown to be strongly related across brain regions in both age groups. Finally, we found metabolic associations between homologous brain regions (SM1 and striatum) in the OA group, with NAA showing a significant correlation between bilateral sensorimotor cortices (SM1) and mIns levels being correlated between the bilateral striata. We posit that a network perspective provides important insights regarding the potential interactions among neurochemicals underlying metabolic processes at a local and global level and their relationship with aging. Funding was provided by: KU Leuven Research Fund (C16/15/070) to SS, DM and OL; the Fonds Wetenschappelijk Onderzoek – Vlaanderen (FWO) (G089818N) to SS and the FWO infrastructure grant to DM and SS; the Excellence of Science (EOS) grant from FWO and the Fonds de la Recherche Scientifique (FNRS) (EOS 30,446,199, MEMODYN) to SS and DM; and EC H2020-MSCA-ITN 2018 INSPiRE-Med (813,120) to UH

Background In 2018 the first Belgian Health Examination Survey (BELHES) took place. The target group included all Belgian residents aged 18 years and older. The BELHES was organized as a second stage of the sixth Belgian Health Interview Survey (BHIS). This paper describes the study design, recruitment method and the methodological choices that were made in the BELHES. Methods After a pilot period during the first quarter of the BHIS fieldwork, eligible BHIS participants were invited to participate in the BELHES until a predefined number (n = 1100) was reached. To obtain the required sample size, 4918 eligible BHIS participants had to be contacted. Data were collected at the participant’s home by trained nurses. The data collection included: 1) a short set of questions through a face-to-face interview, 2) a clinical examination consisting of the measurement of height, weight, waist circumference, blood pressure and for people aged 50 years and older handgrip strength and 3) a collection of blood and urine samples. The BELHES followed as much as possible the guidelines provided in the framework of the European Health Examination Survey (EHES) initiative. Finally 1184 individuals participated in the BELHES, resulting in a participation rate of 24.1%. Results for all the core BELHES measurements were obtained for more than 90% of the participants. Conclusion It is feasible to organize a health examination survey as a second stage of the BHIS. The first successfully organized BELHES provides useful information to support Belgian health decision-makers and health professionals. As the BELHES followed EHES recommendations to a large extent, the results can be compared with those from similar surveys in other EU (European Union) member states.

The hypotheses was: 'There is a decrease in mean reaction time and an increase in the latency of the reaction to the stop signal (SSRT) with a decreased GABA-concentration in elderly as compared to their younger counterparts.' In contrast to the hypothesis the results point out that there is no significant difference in GABA-concentration when younger adults are compared to their older equivalents. In addition to this, no significant differences between both age-groups were found concerning mean reaction time. However, a tendency of a positive correlation between GABA and mean reaction time was found, hypothesizing that younger adults experience faster reaction times in comparison to their older counterparts. Nonetheless, these results were non-significant and need to be interpreted carefully. Ultimately, a significant difference between age-groups was measured considering SSRT, where older adults exhibit a longer SSRT in comparison to their younger counterparts. SSRT and GABA show a tendency of an inverse relationship to each other. However, all the aforementioned results should be interpreted with caution because small sample sizes were used, thus reducing representability. Ultimately, more research is recommended to fully understand the process of motor inhibition.