Vinsamlegast notið þetta auðkenni þegar þið vitnið til verksins eða tengið í það: http://hdl.handle.net/1946/13594
Background: Few studies exist on the validity of food frequency questionnaires (FFQs) administered to elderly people. An FFQ on dietary intake during three different periods of life, adolescence (14-19y), midlife (40-50y) and current old age, was developed for the Age/Gene Environment Susceptibility (AGES) Reykjavik Study. Assessing the validity of the AGES-FFQ is important for its use in studies on diet-related disease risk and health outcomes, as incorrect information may lead to false associations between dietary factors and diseases.
Milk is an important source of calcium and cod liver oil is a traditional source of vitamin D in Iceland. Consumption of both milk and cod liver oil is recommended for people of all ages in Iceland, not the least for the sake of bone health. However, whether and to what extent, lifelong consumption is associated with bone mineral density (BMD) in old age, the time of greatest risk of osteoporotic fractures, is unclear.
The aim of the present thesis was to assess the validity of questions of the AGES-FFQ on midlife and current consumption. Furthermore, to assess the association between lifelong consumption of milk and cod liver oil and hip BMD in old age among participants of the AGES-Reykjavik Study. Also, the association between current intake of cod liver oil and serum 25(OH)D was assessed.
Methods: Data was gathered from three different cohorts. For assessing the validity of questions on midlife diet, retrospective intake of 56-72-year old individuals was estimated using the AGES-FFQ and results compared with detailed dietary data, gathered from the same individuals 18-19 years previously, i.e. in midlife, as a part of a national dietary survey. Validity of questions on current intake was assessed by comparing answers from healthy elderly individuals (≥65y) to data obtained from 3-day weighed food records completed by the same individuals. Participants of the AGES-Reykjavik Study, age 66-96 years (N=4798, 44% male), answered the complete AGES-FFQ, including questions on milk and cod liver oil intake in adolescence, midlife and current old age. BMD of femoral neck and trochanteric area was measured by volumetric quantitative computed tomography (QCT), and serum 25(OH)D concentration measured by means of a direct, competitive chemiluminescence immunoassay. A series of covariates from the AGES Reykjavik Study, as well as the Reykjavik Heart Study were also used in the analysis.
Results: The AGES-FFQ (on midlife and current diet) was found suitable to rank individuals according to intake of several important foods and food groups. Higher correlations were generally found for men than women. Questions on milk and cod liver oil consumption were among those with the highest correlation to the reference methods.
When assessing the association between milk intake at different periods of life and hip BMD in old age, the strongest association was found for midlife consumption, those with consumption of ≥once/day compared with <once/week having significantly higher hip BMD in old age. Women with current consumption of ≥once/day also had significantly higher BMD for trochanter compared with women consuming milk <once/week. Consumption in adolescence showed a similar trend, though insignificant. Associations were generally stronger for men than women.
Retrospective intake of cod liver oil in adolescence and midlife did not show a significant association with hip BMD in old age, neither did current intake for men. However, women with daily intake in current old age, had significantly higher BMD than those with intake of <once/week. Current cod liver oil intake was also associated with serum 25(OH)D concentration, showing increased concentrations with increased frequency of intake.
Conclusion: The AGES-FFQ can be used to rank individuals according to level of intake of several important foods and food groups, including cod liver oil and milk. When assessing the association between milk intake at different periods of life and hip BMD in old age, the strongest association was found for midlife milk intake, and stronger for men than women. Retrospective cod liver oil intake was not associated with hip BMD in old age, neither was current intake for men, while women with daily intakes had significantly higher hip BMD compared to those with intake of <once/week. Current intake was also positively associated with serum 25(OH)D.
Our results underline the importance of identifying critical dietary factors and time periods strongly associated with bone health in old age. Efficient preventive and health promoting measures may thus be developed, improving health, quality of life and independence in old age.
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