To evaluate the validity and reliability of the food frequency questionnaire (FFQ) used in the Shanghai Women's Health Study (SWHS), 200 SWHS participants were recruited for a dietary calibration study. Study participants completed an FFQ at baseline and 24-h dietary recalls (24-HDR) twice per month consecutively for 12 months. At the end of the study, a second FFQ was administered. Of the 200 study participants, 196 completed 24 or more days of 24-h dietary recalls, 191 completed two FFQs from whom the results of this report were based. The FFQ included the foods that accounted for 86% of the foods recorded in the 24-HDR surveys. Validity of the FFQ was evaluated by comparing intake levels of major nutrients and foods obtained from the second FFQ with those derived from the multiple 24-HDR. The median intake for major nutrients, rice, poultry and meat derived from the second FFQ and the 24-HDR was similar, with the differences ranging from 1.3 to 12.1%. The FFQ tended to overestimate the intake level of total vegetables and total fruits, and the differences were explained mainly by over-reporting seasonal vegetables and fruits consumption in the FFQ. Nutrient and food intake assessed by the FFQ and the multiple 24-HDR correlated very well, with the correlation coefficients being 0.59-0.66 for macronutrients, 0.41-0.59 for micronutrients, and 0.41-0.66 for major food groups. The reliability of the FFQ was assessed by comparing the correlation and median intake of nutrients and food groups obtained from the two FFQs that were administered approximately 2 y apart. The median intake levels for selected nutrients and food groups derived from the two FFQs were similar with differences below 10%. At the individual level, the intake levels of these dietary variables obtained from two FFQs also correlated well. When nutrient and food group intakes were categorized into quartiles, FFQ and 24-HDR produced exact agreement rates between 33 and 50%. Misclassification to adjacent quartile was common, ranging from 34-48%, while misclassification to an extreme quartile was rare (1-6%). These data indicate that the SWHS FFQ can reliably and accurately measure usual intake of major nutrients and food groups among women in Shanghai.
Purpose of the study
To examine the effect of late-life body mass index (BMI) and rapid weight loss on incident mild cognitive impairment (MCI) and Alzheimer’s disease (AD)
Design
Prospective longitudinal cohort study
Setting
National Alzheimer’s Coordinating Center (NACC) Uniform Data Set, including 34 past and current National Institute on Aging-funded AD Centers across the United States
Participants
6940 older adults (n=5061 normal cognition (NC); n=1879 MCI)
Measurements
BMI (kg/m2) and modified Framingham Stroke Risk Profile (FSRP) score (sex, age, systolic blood pressure, anti-hypertension medication, diabetes mellitus, cigarette smoking, prevalent cardiovascular disease, atrial fibrillation) were assessed at baseline. Cognition and weight were assessed annually.
Results
Multivariable binary logistic regression, adjusting for age, sex, race, education, length of follow-up, and modified FSRP related late-life BMI to risk of diagnostic conversion from NC to MCI or AD and from MCI to AD. Secondary analyses related late-life BMI to diagnostic conversion in the presence of rapid weight loss (>5% decrease in 12 months) and apolipoprotein E (APOE) ε4. During a mean 3.8-year follow-up period, 12% of NC participants converted to MCI or AD and 49% of MCI participants converted to AD. Higher baseline BMI was associated with a reduced probability of diagnostic conversion, such that for each one-unit increase in baseline BMI there was a reduction in diagnostic conversion for both NC (OR=0.977, 95%CI 0.958–0.996, p=0.015) and MCI participants (OR=0.962, 95%CI 0.942–0.983, p<0.001). The protective effect of higher baseline BMI did not persist in the setting of rapid weight loss but did persist when adjusting for APOE.
Conclusions
Higher late-life BMI is associated with a lower risk of incident MCI and AD but is not protective in the presence of rapid weight loss.
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