| 2. |
- van Bakel, Marit M E, et al.
(author)
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Methodological challenges in the application of the Glycemic Index in epidemiological studies using data from the European prospective investigation into cancer and nutrition
- 2009
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In: Journal of Nutrition. - : Elsevier BV. - 0022-3166 .- 1541-6100. ; 139:3, s. 568-575
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Journal article (peer-reviewed)abstract
- Associations between the glycemic index (GI) or glycemic load (GL) and diseases are heterogeneous in epidemiological studies. Differences in assigning GI values to food items may contribute to this inconsistency. Our objective was to address methodological issues related to the use of current GI and GL values in epidemiological studies. We performed ecological comparison and correlation studies by calculating dietary GI and GL from country-specific dietary questionnaires (DQ) from 422,837 participants from 9 countries participating in the European Prospective Investigation into Cancer and Nutrition study and single standardized 24-h dietary recalls (24-HDR) obtained from a representative sample (n = 33,404) using mainly Foster Powell's international table as a reference source. Further, 2 inter-rater and 1 inter-method comparison were conducted, comparing DQ GI values assigned by independent groups with values linked by us. The ecological correlation between DQ and 24-HDR was good for GL (overall r = 0.76; P < 0.005) and moderate for GI (r = 0.57; P < 0.05). Mean GI/GL differences between DQ and 24-HDR were significant for most centers. GL but not GI from DQ was highly correlated with total carbohydrate (r = 0.98 and 0.15, respectively; P < 0.0001) and this was higher for starch (r = 0.72; P < 0.0001) than for sugars (r = 0.36; P < 0.0001). The inter-rater and inter-method variations were considerable for GI (weighted kappa coefficients of 0.49 and 0.65 for inter-rater and 0.25 for inter-method variation, respectively) but only mild for GL (weighted kappa coefficients > 0.80). A more consistent methodology to attribute GI values to foods and validated DQ is needed to derive meaningful GI/GL estimates for nutritional epidemiology.
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| 3. |
- Cust, Anne E, et al.
(author)
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The influence of overweight and insulin resistance on breast cancer risk and tumour stage at diagnosis : a prospective study.
- 2009
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In: Breast Cancer Research and Treatment. - : Springer. - 0167-6806 .- 1573-7217. ; 113:3, s. 567-576
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Journal article (peer-reviewed)abstract
- It is hypothesized that insulin resistance and related metabolic factors may influence breast cancer risk, however the epidemiological evidence remains inconclusive. We conducted a case–control study nested in a prospective cohort in Northern Sweden, to clarify the associations of body mass index (BMI), leptin, adiponectin, C-peptide, and glycated haemoglobin (HbA1c) with breast cancer risk. We also investigated whether these associations may be modified by age at diagnosis, tumour stage, and oestrogen and progesterone receptor status. During follow-up, 561 women developed invasive breast cancer and 561 matched controls were selected. Conditional logistic regression was used to calculate odds ratios (OR) as estimates of relative risk, and 95% confidence intervals (CI). The associations of BMI, leptin and HbA1c with breast cancer risk differed significantly according to whether the tumour was diagnosed as stage I or stage II–IV (P heterogeneity all <0.05). These factors were significantly inversely associated with risk in the group of stage I tumours, with ORs for top vs. bottom tertile for BMI of 0.48 (95% CI, 0.30–0.78, P trend = 0.004); leptin, 0.64 (95% CI, 0.41–1.00, P trend = 0.06); and HbA1c, 0.47 (95% CI, 0.28–0.80, P trend = 0.005). For stage II–IV tumours, there was a suggestion of an increased risk with higher levels of these factors. There were no significant differences in the associations of BMI, leptin, adiponectin, C-peptide and HbA1c with breast cancer risk in subgroups of age at diagnosis or tumour receptor status. This prospective study suggests that BMI, leptin and HbA1c influence breast tumour initiation and progression.
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