With much interest we read the paper of Waldstein and Katzel in this journal.1 They investigated relationships between vascular risk factors and cognitive performance in 90 older persons. Higher waist circumference (WC) and blood pressure (BP) showed both main and multiplicative effects on several cognitive performance tests. These results seem to support the role of a vascular mechanism in age-related cognitive deficits, as suggested by the authors. Individuals with vascular disease, such as diabetes, had been excluded from their sample, which makes their findings even more noteworthy, owing to their potential clinical implications. We noted, however, that these results were not in line with those obtained from our own work in the Maastricht Aging Study (MAAS). In an earlier study in 936 healthy persons aged between 24 and 81 years we found no main effects of BP on several domains of neuropsychological performance, including verbal memory and cognitive flexibility.2 Furthermore, a measure of central obesity, expressed as waist-to-hip ratio, also showed no association with cognitive variables, after correction for demographic influences. As the population, design and methods of the Waldstein et al. study were quite similar to MAAS, we tried to replicate their findings, but on a larger dataset of 488 persons of almost identical vascular risk profile and demographical makeup. Cognition was tested with conceptually the same instruments as used in the Waldstein study.
Mean values of obesity indicators BMI and WC were comparable with the Waldstein study (BMI 27.5 vs 27.4 kg/m2 and WC 91.4 vs 91.8 cm, in the Waldstein sample and MAAS, respectively). However, again we found no main effects of BP, WC or BMI on the three cognitive variables studied, that is, verbal memory (word learning test), perceptuomotor speed and mental flexibility (Stroop and Concept Shifting tests). Furthermore, no interactions were present between BP and obesity indicator on test performance. A more detailed account of the methods and results cannot be given here owing to space constraints, but can be obtained by sending an email to the author of this letter.
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