The association of total cholesterol with processing speed is moderated by age in mid- to late-age healthy adults

Physical fitness mediates the association between age and cognition in healthy adults

BACKGROUND

Physical fitness is an important contributor to healthy aging that improves cognition. Older adults who engage in cardiorespiratory fitness activities show less cognitive decline.

AIMS

To examine whether physical fitness acts as a potential protective mechanism shielding against the negative associations between age and cognition. Specifically, we examined whether physical fitness mediates the relationship between age and processing speed.

METHODS

114 (M = 63.80, SD = 10.63) senior executives completed a computerized cognitive battery composed of four processing speed tasks. Level of physical fitness was assessed on a treadmill stress test and reported in metabolic equivalents (METs).

RESULTS

Older age was associated with slower processing speed (r = 0.25, p = 0.007), whereas greater physical fitness was associated with faster processing speed (r = -0.30, p = 0.001). Path analysis indicated that the association between age and processing speed was fully mediated by the level of physical fitness (Indirect effect: β = 0.10, p = 0.008; Direct effect: β = 0.16, p = 0.20).

CONCLUSIONS AND DISCUSSION

The findings indicate that physical fitness is a strong mediator of the relationship between age and processing speed and imply that physical fitness makes a major contribution to cognitive reserve during the aging process. The results may suggest that the decrease in physical fitness during aging may partially account for slower cognitive processing.

Interaction of maternal immune activation and genetic interneuronal inhibition

Genes and environment interact during intrauterine life, and potentially alter the developmental trajectory of the brain. This can result in life-long consequences on brain function. We have previously developed two transgenic mouse lines that suppress Gad1 expression in parvalbumin (PVALB) and neuropeptide Y (NPY) expressing interneuron populations using a bacterial artificial chromosome (BAC)-driven miRNA-based silencing technology. We were interested to assess if maternal immune activation (MIA), genetic interneuronal inhibition, and the combination of these two factors disrupt and result in long-term changes in neuroinflammatory gene expression, sterol biosynthesis, and acylcarnitine levels in the brain of maternally exposed offspring. Pregnant female WT mice were given a single intraperitoneal injection of saline or polyinosinic-polycytidilic acid [poly(I:C)] at E12.5. Brains of offspring were analyzed at postnatal day 90. We identified complex and persistent neuroinflammatory gene expression changes in the hippocampi of MIA-exposed offspring, as well in the hippocampi of Npy/Gad1 and Pvalb/Gad1 mice. In addition, both MIA and genetic inhibition altered the post-lanosterol sterol biosynthesis in the neocortex and disrupted the typical acylcarnitine profile. In conclusion, our findings suggest that both MIA and inhibition of interneuronal function have long-term consequences on critical homeostatic mechanisms of the brain, including immune function, sterol levels, and energy metabolism.

Increases in total cholesterol and low density lipoprotein associated with decreased cognitive performance in healthy elderly adults

The current study examined associations between blood lipid profiles and cognitive functioning using a healthy non-demented elderly sample. The sample comprised 196 healthy volunteers (male; 86: female 110) aged 60-75 years from the Australian Research Council Longevity Intervention (ARCLI) study cohort. Serum total cholesterol (T-C), low density lipoprotein cholesterol (LDL-c), high density lipoprotein cholesterol (HDL-c) and triglycerides (TGL) were collected, and participants completed the Swinburne University Computerized Cognitive Assessment Battery (SUCCAB). In line with prediction, higher levels of T-C and LDL-c were found to be associated with impaired speeds of response in tasks assessing recognition memory, working memory and inhibitory processing. However, contrary to prediction both TGL and HDL-c were found to be unrelated to cognitive functioning in the current sample. It is suggested that frontal lobe function may be differentially sensitive to the effects of T-C and LDL-c accumulation during the aging process. Future data collection as part of the larger ARCLI intervention study will provide important follow-up data regarding the ability of the baseline blood lipid data to predict subsequent cognitive change.