H. Bosma

Inflammation markers in relation to cognition in a healthy aging population.

The relation between serum inflammatory protein levels and cognitive performance was investigated in a healthy population. Individuals were tested during 6 years of follow-up. Serum concentrations of 10 inflammatory proteins were correlated to cognitive speed (Letter-Digit Coding Test, LDCT), attention and information processing (Stroop) and memory (Word Learning). Haptoglobin levels at baseline correlated negatively with cognitive performance on the Stroop and Word Learning Recall test over the 6 years follow-up period. C-reactive protein (CRP) levels at baseline correlated negatively with performance on the Word Learning tests over the 6 years follow-up period. Thus, relatively high concentrations of haptoglobin and C-reactive protein may be indicative for impaired cognitive performance.

Predictors of attrition in a longitudinal cognitive aging study: the Maastricht Aging Study (MAAS).

A large sample of older participants of the Maastricht Aging Study (MAAS) were compared to drop-outs at the 3-year follow-up with respect to socio-demographic, health, and cognitive characteristics. In addition, the impact of selective drop-out on measures of cognitive change was examined. To this end, hypothetical scores were estimated for drop-outs by using single and multiple imputation methods. Of the initial sample of 539 subjects, aged 49 years and older at baseline, 116 (22 %) did not return for the follow-up (n = 32 had died, n = 84 refused participation). Drop-outs who refused to participate in the follow-up were more often women, had lower educational levels, and had lower baseline scores on neurocognitive tests. Follow-up drop-outs who had died were more often men, older, and had a poorer performance on cognitive tests than the follow-up participants. Although follow-up participants and drop-outs differed in terms of socio-demographic and cognitive characteristics, attrition appeared to have little effect on the estimates of cognitive change.

Combination of serum markers related to several mechanisms in Alzheimer’s disease

Alzheimers disease (AD) probably involves several pathobiochemical mechanisms and this may be reflected by changes in different serum components. The present study investigated whether the combined analysis of serum molecules related to different mechanisms improves the discrimination of AD patients from healthy controls. Serum of patients with AD was analyzed for a broad spectrum of marker molecules, including 11 inflammatory proteins, 12 sterol intermediates and phytosterols, 2 brain-specific proteins and 4 constituents involved in homocysteine homeostasis. The serum molecule concentrations were combined in a logistic regression model, using a forward stepwise inclusion mode. The results showed that the combination of interleukin-6 (IL-6) receptor, protein alpha1 fraction, cysteine and cholesterol concentrations improved the discrimination between AD patients and healthy controls compared to the single markers. In conclusion, the results of this study have shown that the complex pathology in AD is reflected in a pattern of altered serum concentrations of several marker molecules related to several pathobiochemical mechanisms.

Serum cholesterol, precursors and metabolites and cognitive performance in an aging population

The present study investigated if a causal relation exists between serum concentrations of precursors and metabolites of cholesterol and cognitive performance in a healthy aging population. Cognitive function addressing four domains of 144 individuals (30-80 years) was tested at baseline and after 6 years of follow-up. Serum concentrations of different sterols related to cholesterol were measured. Serum levels of lathosterol and lanosterol correlated negatively with cognitive performance on the Word Learning tests for verbal learning and memory. This was observed at baseline and follow-up and was independent of age, sex and educational level. Furthermore, the levels of lathosterol and lanosterol at baseline correlated with performance on the Stroop test and Word Learning tests over the 6-year follow-up period. Serum levels of 27-hydroxycholesterol and 24S-hydroxycholesterol showed inconsistent correlations, while cholesterol, desmosterol, sitosterol and campesterol were not related to cognitive performance.Thus, relative high serum ratios of the cholesterol precursors lanosterol and lathosterol, indicative for a high rate of endogenous cholesterol synthesis, are associated with relatively low memory performance in this aging population.

Pesticide exposure and risk of mild cognitive dysfunction

Little is known about the adverse effects of substances, such as pesticides and metals, on the development of mild cognitive dysfunction (MCD). Cross-sectional and prospective data from the Maastricht Aging Study were used to find out the potential neurotoxicity of particular substances. Exposure to pesticides, for example by arable farmers and gardeners, was associated with increased risks of MCD. Exposure to metals and organic solvents was not associated with MCD. Our findings might reflect subtle changes in brain function among people exposed to pesticides.

Neuroticism does not affect cognitive functioning in later life

In a cross-sectional study, Jorm and colleagues (1993. Personality and Individual Differences, 15, 721-723) found that neuroticism was related to poorer cognitive performance in the elderly. The present study was initiated to expand their findings using both cross-sectional and longitudinal data from the Maastricht Aging Study. In contrast to the findings of Jorm and coworkers, neuroticism was not associated with either current cognitive performance or cognitive decline over a period of 3 years.

Predictors of attrition in a longitudinal cognitive aging study: the Maastricht Aging Study

A large sample of older participants of the Maastricht Aging Study (MAAS) were compared to drop-outs at the 3-year follow-up with respect to socio-demographic, health, and cognitive characteristics. In addition, the impact of selective drop-out on measures of cognitive change was examined. To this end, hypothetical scores were estimated for drop-outs by using single and multiple imputation methods. Of the initial sample of 539 subjects, aged 49 years and older at baseline, 116 (22 %) did not return for the follow-up (n = 32 had died, n = 84 refused participation). Drop-outs who refused to participate in the follow-up were more often women, had lower educational levels, and had lower baseline scores on neurocognitive tests. Follow-up drop-outs who had died were more often men, older, and had a poorer performance on cognitive tests than the follow-up participants. Although follow-up participants and drop-outs differed in terms of socio-demographic and cognitive characteristics, attrition appeared to have little effect on the estimates of cognitive change.

Predictors of attrition in a longitudinal cognitive aging study

A large sample of older participants of the Maastricht Aging Study (MAAS) were compared to drop-outs at the 3-year follow-up with respect to socio-demographic, health, and cognitive characteristics. In addition, the impact of selective drop-out on measures of cognitive change was examined. To this end, hypothetical scores were estimated for drop-outs by using single and multiple imputation methods. Of the initial sample of 539 subjects, aged 49 years and older at baseline, 116 (22 %) did not return for the follow-up (n = 32 had died, n = 84 refused participation). Drop-outs who refused to participate in the follow-up were more often women, had lower educational levels, and had lower baseline scores on neurocognitive tests. Follow-up drop-outs who had died were more often men, older, and had a poorer performance on cognitive tests than the follow-up participants. Although follow-up participants and drop-outs differed in terms of socio-demographic and cognitive characteristics, attrition appeared to have little effect on the estimates of cognitive change.