Women (n 160) aged 50 to 65 years were asked to weigh their food for 4 d on four occasions over the period of 1 year, using the PETRA (Portable Electronic Tape Recorded Automatic) scales. Throughout the year, they were asked to complete seven other dietary assessment methods: a simple 24 h recall, a structured 24 h recall with portion size assessments using photographs, two food-frequency questionnaires, a 7 d estimated record or open-ended food diary, a structured food-frequency (menu) record, and a structured food-frequency (menu) record with portion sizes assessed using photographs. Comparisons between the average of the 16 d weighed records and the first presentation of each method indicated that food-frequency questionnaires were not appreciably better at placing individuals in the distribution of habitual diet than 24 h recalls, due partly to inaccuracies in the estimation of frequency of food consumption. With a 7 d estimated record or open-ended food diary, however, individual values of nutrients were most closely associated with those obtained from 16 d weighed records, and there were no significant differences in average food or nutrient intakes.
Dietary assessment methods: Weighed intake : Nutritional epidemiologyRecognition of the need for prospective investigation of future individual risk of cancer, and other diseases of middle life, in relation to present day diet is one of the factors that has prompted the search for accurate measures of habitual diet. However, the methodological aims of nutritional epidemiology are inevitably tempered by two opposing interests: that of accuracy in the dietary assessment, and that of feasibility for use in large numbers of individuals, in order to have sufficient power to detect modest relative risks and to demonstrate doseresponse relationships (Bingham, 1987). As part of the preparation for a large European collaborative study of diet and cancer risk (EPIC, European Prospective Investigation of Cancer) we have therefore assessed the accuracy of various methods commonly used in epidemiological studies of diet in large numbers of subjects. We assessed the accuracy of each method by comparison with 16 d of weighed records kept over 1 year.
UK EPIC uses three methods (the 7-day diary, an improved FFQ, and the 24-hour recall) to assess diet. 93% of first food diaries are returned completed by participants. Repeated diaries are the main dietary assessment method for nested case-control analyses.
The CAMCOG, which forms part of the CAMDEX interview (Roth et a/., 1986, 1988), is a brief neuropsychological battery designed to assess the range of cognitive functions required for a diagnosis of dementia, and to detect mild degrees of cognitive impairment. It was administered to a population sample of 418 elderly people (aged 77 and above) in their place of residence. The data show that in contrast to the Mini-Mental State Examination, total CAMCOG scores are well distributed and there is no ceiling effect.Examination of the association between CAMCOG scores and socio-demographic variables (age, sex, education and social class) shows that each exerts a significant, and independent, effect upon performance.CAMCOG also includes a number of subscales which assess individual areas of cognitive function. Of the eight major subscales (orientation, language, memory, attention, praxis, calculation, abstract thinking, perception), age was significantly related to all but attention ; sex with attention, praxis, calculation and perception; education with language and abstract thinking; and social class with language and perception. In all these analyses, the results were adjusted for the effects of the other socio-demographic variables using analysis of variance. However, education and social class are highly correlated variables and when the association with education is examined without adjusting for social class, attention and praxis are also found * Requests for reprints.
The findings show high rates of new onset dementia, increasing markedly with age, and suggest rapid acceleration of one or more processes that is common in advanced age.
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