Jean-Claude Marquié

Relation between body mass index and cognitive function in healthy middle-aged men and women

Objective: To assess whether body mass index (BMI) is associated with cognitive function and cognitive decline in healthy men and women. Methods: In this prospective cohort study, we analyzed data from 2,223 healthy workers aged 32 to 62 years at baseline. Medical, psychosocial, and environmental data were collected in 1996 and in 2001. We tested cognitive functions at baseline and at follow-up with word-list learning (four recalls), a Digit–Symbol Substitution Test, and a selective attention test. Results: Cross-sectionally, a higher BMI was associated with lower cognitive scores after adjustment for age, sex, educational level, blood pressure, diabetes, and other psychosocial covariables. A higher BMI at baseline was also associated with a higher cognitive decline at follow-up, after adjustment for the above-cited confounding factors. This association was significant for word-list learning. For the changes in scores at word-list learning (delayed recall), regression coefficients were −0.008 ± 0.13, −0.09 ± 0.13, −0.17 ± 0.14, and −0.35 ± 0.14 (p for trend < 0.001) for the second, third, fourth, and fifth quintiles of BMI at baseline when compared with the first quintile. No significant association was found between changes in BMI and cognitive function. Conclusions: Body mass index was independently associated both with cognitive function (word-list learning and Digit–Symbol Substitution Test) and changes in word-list learning in healthy, nondemented, middle-aged men and women.

Do older adults underestimate their actual computer knowledge

This work examined the hypothesis that elderly people are less confident than young people in their own computer knowledge. This was done by having 49 young (M = 22.6 years) and 42 older (M = 68.6 years) participants to assess their global self-efficacy beliefs and to make item-by-item prospective (feeling-of-knowing: FOK) and retrospective (confidence level: CL) judgments about their knowledge in the two domains of computers and general knowledge. The latter served as a control domain. Item difficulty was equated across age groups in each domain. In spite of this age equivalence in actual performance, differences were found in FOK and CL ratings for computers but not for general knowledge, with older people being less confident than young people in their own computer knowledge. The greater age difference in ratings observed in the computer domain, as compared with the general domain, was even greater for the FOK than for the CL judgments. Statistical control of age differences in global self-efficacy beliefs in the computer domain (poorer in the older participants, but not in the general domain), eliminated age differences in FOK and CL judgments in the same domain. These findings confirm earlier ones. They suggest that underconfidence in their relevant abilities is one possible source of the difficulties that the elderly may encounter in mastering new computer technologies.

Shiftwork experience, age and cognitive performance

Changes of alertness and cognitive efficiency has been suggested in people whose circadian rhythms are disrupted, e.g. night or shift-workers. Data from field and laboratory studies have demonstrated short-term cognitive disturbances related to circadian rhythm disruption. By contrast, little is known about the long-term consequences of chronic sleep deprivation, as can be observed with shift-work, on cognitive abilities. The present paper is aimed at evaluating, on a large cross-sectional sample of workers, the long-term influence of shift-work on verbal memory and speed performances. Participants were 3237 workers aged 32, 42, 52, and 62 years of various occupational statuses included in the VISAT (Aging, Health and Work) cohort. Data collected by questionnaires included items on working hours and shift-work and sleep disorders. Cognitive abilities were assessed using neuropsychological tests. Current male shift-workers had lower cognitive performance than never exposed workers. In the same population, memory performance tended to decrease with increasing shift-work duration. Among former shift-workers, the cognitive performance of the participant having stopped shiftwork more than 4 years ago seemed to be increased, suggesting a possible reversibility of effects. In conclusion, this study demonstrated that cognitive functioning tends to be impaired by a long-term exposure to SW. As found by other authors, neuropsychological performance tends to decrease with the increases in the duration of exposure to SW.

Shift work and cardiovascular risk factors : New knowledge from the past decade

Cardiovascular diseases remain a major public health problem. The involvement of several occupational factors has recently been discussed, notably the organization of work schedules, e.g. shift work. To analyse the progress of knowledge on the relationship between cardiovascular risk factors and shift work. A review of English-language literature dealing with the link between cardiovascular factors and shift workers (published during 2000-2010) was conducted. Studies published in the past 10 years tend to document an impact of shift work on blood pressure, lipid profile (triglyceride levels), metabolic syndrome and, possibly, body mass index. However, the consequences on glucose metabolism are unclear. These results are not yet firmly established, but are supported by strong hypotheses. Some advice could reasonably be proposed to guide the clinical practitioner.

Environmental factors associated with body mass index in a population of Southern France

Study objective Environmental-factor changes may largely be accountable for the dramatic increase of obesity prevalence in industrialized countries. This study investigated the relationships between body mass index (BMI) and various socioeconomic, clinical, behavioural and reproductive factors in a population from Southern France. Methods Using a cross-sectional study, a sample of 3127 current and former salaried workers (1658 men and 1469 women) completed a questionnaire on personal and medical histories, and had a clinical examination including height and weight measurements. Age-adjusted and multiple linear regression analyses were performed. Results The overall prevalence of obesity (BMI ≤ 30kg/m2) was 9.8% and was higher in men than in women (11.1 versus 8.3%). Multivariate analyses showed that in both sexes, low educational level, television watching, low physical activity and ex-smoking habits, were independently associated with a higher BMI. Furthermore, in women, we found independent and positive associations between BMI and the number of naps per week, short sleep duration, daily alcohol consumption, the number of pregnancies, early age at menarche or the non-use of oral contraceptives. Conclusions Our results reveal the complexity that exists between BMI and environmental factors and stress the need to analyse and to handle these factors simultaneously.

Chronic effects of shift work on cognition: findings from the VISAT longitudinal study

Objectives Shift work, like chronic jet lag, is known to disrupt workers’ normal circadian rhythms and social life, and to be associated with increased health problems (eg, ulcers, cardiovascular disease, metabolic syndrome, breast cancer, reproductive difficulties) and with acute effects on safety and productivity. However, very little is known about the long-term consequences of shift work on cognitive abilities. The aim of this study was to assess the chronicity and reversibility of the effects of shift work on cognition. Methods We conducted a prospective cohort study of 3232 employed and retired workers (participation rate: 76%) who were 32, 42, 52 and 62 years old at the time of the first measurement (t1, 1996), and who were seen again 5 (t2) and 10 (t3) years later. 1484 of them had shift work experience at baseline (current or past) and 1635 had not. The main outcome measures were tests of speed and memory, assessed at all three measurement times. Results Shift work was associated with impaired cognition. The association was stronger for exposure durations exceeding 10 years (dose effect; cognitive loss equivalent to 6.5 years of age-related decline in the current cohort). The recovery of cognitive functioning after having left shift work took at least 5 years (reversibility). Conclusions Shift work chronically impairs cognition, with potentially important safety consequences not only for the individuals concerned, but also for society.

Higher mental stimulation at work is associated with improved cognitive functioning in both young and older workers

The study examined whether mental stimulation received in the workplace positively affects cognitive functioning and rate of cognitive change. Data taken from the VISAT (ageing, health and work) longitudinal study concerned 3237 workers who were seen three times (in 1996, 2001 and 2006) and who were aged between 32 and 62 years at baseline. Measures of cognitive stimulation both at work and outside work were available at baseline. Cognitive efficiency was assessed on the three occasions through episodic verbal memory, attention and processing speed tests. Greater cognitive stimulation (at work and outside work) was associated with higher levels of cognitive functioning and a more favourable change over the 10-year follow-up. These results were obtained after adjustment for age, education, sex and a variety of medical, physical and psychosocial confounders. The study thus supports the hypothesis that exposure to jobs that are mentally demanding and that offer learning opportunities increases the level of cognitive functioning and possibly attenuates age-related decline. Statement of Relevance: The effect of occupational activity on cognitive functioning is under-researched. This paper reports results from a substantive longitudinal study, with findings indicating that exposure to jobs that are mentally demanding are beneficial in increasing levels of cognitive functioning and possibly attenuating age-related decline.

Age differences in feeling-of-knowing and confidence judgments as a function of knowledge domain.

For two semantic knowledge domains, general and computer-related, feeling-of-knowing (FOK) and confidence level (CL) ratings and their relative accuracy were assessed in young, middle-aged, and older adults, after test difficulty was equated across age groups. Global memory self-efficacy beliefs were also assessed for each domain. As expected, greater age was associated with poorer memory self-efficacy beliefs only in the computer domain. The oldest two groups were found to be more underconfident than young adults when rating their FOK but not their CL, for computer items but not for general items. Statistical control of age differences in memory self-efficacy beliefs in the relevant domain greatly reduced this age effect on computer-related FOK ratings. This finding suggests that absolute FOK judgments are more closely related to memory self-efficacy beliefs than are CL judgments. Gamma correlations between judgments and recognition performance revealed that all age groups were equally accurate in FOK and in CL judgments, in both domains.

Relationship Between Markers of Insulin Resistance, Markers of Adiposity, HbA1c, and Cognitive Functions in a Middle-Aged Population–Based Sample: the MONA LISA Study

OBJECTIVE To determine the relationship between markers of insulin resistance (fasting insulin and homeostasis model assessment of insulin resistance), markers of adiposity (BMI, waist circumference, and body fat), HbA1c, and cognitive performances in a middle-aged population–based sample free of diabetes. RESEARCH DESIGN AND METHODS Our study sample consisted of 1,172 people aged 35–64 years (49% women), free of diabetes, and recruited between 2005 and 2007 in the MONA LISA survey. Cognitive functions (memory, attention, and processing speed) were evaluated by neuropsychological tests: word-list learning test, digit symbol substitution test (DSST), word fluency test, and Stroop Test. Multiple logistic regressions were used to estimate the relationship between cognitive performance and metabolic markers. We serially adjusted for age, sex, education, and occupational status (model A), additionally for income, smoking, alcohol consumption, sedentarity, and psychotropic substance use (model B), and finally, included variables linked to the metabolic syndrome (hypertension, dyslipidemia, vascular disease, and C-reactive protein) and depression (model C). RESULTS Elevated markers of adiposity were associated with poor cognitive performance in tests evaluating processing speed. The probability of being in the lowest quartile of each test was nearly doubled for participants in the upper quartile of BMI, compared with those in the lowest one [BMI, adjusted odds ratio (OR) 2.18, P = 0.003 (DSST), and OR 2.09, P = 0.005 (Stroop Test)]. High HbA1c was associated with poor cognitive performance in DSST (adjusted OR 1.75, P = 0.037). Waist circumference was linked to poor cognitive performance in men but not in women. CONCLUSIONS Poor cognitive performance is associated with adiposity and hyperglycemia in healthy middle-aged people.

Strategy and accuracy during information search on the Web

This study focused on the impact of question complexity and age on information search activity.10 older and 10 younger adults had to answer questions in using a search engine.Younger adults gave more correct answers than older ones for complex questions.Older adults developed fewer efficiency strategies than younger adults.Age-related differences were particularly pronounced for complex questions. The present study addressed age-related differences in performance and strategies while searching for information on the Web while considering specific processes involved in the search activity on the Internet. To this end, 10 older and 10 younger adults were instructed to use Google to find information. The search questions varied and increased in complexity: three simple questions (participants had to use the keywords provided in the questions), three difficult questions (participants had to infer new keywords to find correct answers), and three impossible questions (no answer existed). The results showed that older participants were less accurate and used fewer efficient strategies compared to younger participants. The differences increased as a function of question complexity. Moreover, older participants tended to focus on the evaluation of the results provided by Google at the expense of opening up and examining websites. In contrast, younger participants controlled their own activities more often, thus allowing them to improve their strategies and obtain higher performances, contrary to older participants who used the same strategies regardless the complexity of the search question.