UWL: Association With Outcomes (2009)

Study Design:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To investigate whether under- or overweight and weight change is associated with cognitive performance of elderly citizens.

Inclusion Criteria:
  • Basel Study Cohort participants
  • Free-living nondemented elderly population
  • Included if complete data sets of the following measurements were available:
    • Follow-up 1965: Height measurement
    • Follow-up 1990: Body weight
    • Follow-up 2000: Body weight, blood pressure, diabetes status, apolipoprotein E (ApoE) genotype and the CERAD-NAB.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:


Participants were taken from the Basel Study Cohort, a convenience sample of workers and employees of four large chemical and pharmaceutical companies in Basel, Switzerland.


Prospective cohort study. 

Statistical Analysis

  • The effect of ApoE genotype on annual change in BMI was tested by means of ANOVA
  • The predictive power of the annual change in BMI with cognitive performance was investigated with a binary logistic regression analysis (backward) using sex, age, BMI in 1990, BMI in 2000, diastolic blood pressure, diabetes status and optimal health status as additional predictors.
Data Collection Summary:

Timing of Measurements

Baseline measurements taken in 1960 with follow-up examinations in 1965, 1971, 1990 and 2000. Subjects were assessed with the CERAD-NAB in 2000 and weight measurements were obtained in 1990 and 2000.

Dependent Variables

  • Cognitive performance was assessed with the Consortium to Establish a Registry for Alzheimer's Disease-Neuropsychological Assessment Battery (CERAD-NAB)
  • This battery consists of five tests that are administered in eight steps; 11 meaningful scores were extracted.

Independent Variables

  • Annual change in BMI was calculated from 1990 to 2000 based on weight measurements 
  • 1990 weight based on self-reported questionnaire
  • Optimal health was defined as no current systemic illnesses, no diseases interfering with the administration of CERAD-NAB, no psychiatric problems, no diseases of the central nervous system and no diseases or events that could negatively impact on central nervous system activity
  • ApoE genotype.

Control Variables

  • Age
  • Sex
  • Education.
Description of Actual Data Sample:
  • Initial N: 531 healthy subjects fulfilled inclusion criteria (445 males, 86 females)
  • Attrition (final N): As above
  • Age: Mean age, 69.4±7.8 years in 2000
  • Location: Switzerland.
Summary of Results:

Odds Ratios for Having Poor Cognitive Performance and 95% Confidence Intervals



Odds Ratio

95% CI

ApoE-ε4 noncarriers

413 1  
ApoE-ε4 carriers 118 1.68 1.01 to 2.78 
Optimally healthy 303 1  

Not optimally healthy



1.30 to 3.24 

Other Findings

  • The weight history patterns differed significantly between men and women (P<0.01)
  • More women gained weight compared with men, while more men lost weight compared with women
  • The annual change in BMI differed significantly between the 75-year-old and older subjects and the younger population (P<0.01)
  • Moreover, the weight history patterns differed significantly between the two age groups (P<0.01)
  • No difference in the annual change in BMI between ApoE genotypes could be found (P=0.18)
  • In the last step, the following variables remained in the model: Annual change in BMI (quadratic term; P<0.01); ApoE genotype (P<0.05); and optimal health status (P<0.01).
Author Conclusion:

The association between weight change and cognitive performance could be interpreted either as a consequence of cognitive impairment or as an early symptom of neurodegenerative decline. Weight change could very well be a symptom of less control for appetite. Our study suggests that elderly persons should maintain body weight consciously. However, keeping patients' with Alzheimer's disease body weight in balance may prove to be of clinical importance because weight loss is, in fact, associated with higher mortality and a substantial weight gain in the elderly population may increase the prevalence and severity of cardiovascular risk factors such as hypertension, diabetes, and hyperlipidemia.

Funding Source:
Novartis Research Foundation
Foundation associated with industry:
Other: SNF Grant #3200-049107
Reviewer Comments:

This study demonstrates that for both weight loss and weight gain there is a worsening of cognition. The Basel Study Cohort was a convenience sample of workers and employees of four large chemical and pharmaceutical companies, representative of Swiss working class. Weight was based on self-report. Authors note the following limitations:

  • Owing to osteoporosis or for other orthopaedic reasons, height may change significantly during the lifetime and therefore the BMI calculations may not be useful
  • 1990 weight based on self-report questionnaire.
Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) N/A
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) N/A
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? ???
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? N/A
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? N/A
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) N/A
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? N/A
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) N/A
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? Yes
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? N/A
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? N/A
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? N/A
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? ???
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? No
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes