Dietary glycaemic index and cognitive function: prospective associations in adults of the 1946 British birth cohort.

OBJECTIVE: Evidence suggests that the rate of glucose release following consumption of carbohydrate-containing foods, defined as the glycaemic index (GI), is inversely associated with cognitive function. To date, most of the evidence stems from either single-meal studies or highly heterogeneous cohort studies. We aimed to study the prospective associations of diet GI at age 53 years with outcomes of verbal memory and letter search tests at age 69 years and rate of decline between 53 and 69 years. DESIGN: Longitudinal population-based birth cohort study. SETTING: MRC National Survey for Health and Development. PARTICIPANTS: Cohort members (n 1252). RESULTS: Using multivariable linear and logistic regression, adjusted for potential confounders, associations of higher-GI diet with lower verbal memory, lower letter search speed and lower number of hits in a letter search test were attenuated after adjustments for cognitive ability at age 15 years, educational attainment, further training and occupational social class. No association was observed between diet GI at 53 years and letter search accuracy or speed-accuracy trade-off at 69 years, or between diet GI at 53 years and rate of decline between 53 and 69 years in any cognitive measure. CONCLUSIONS: Diet GI does not appear to predict cognitive function or decline, which was mainly explained by childhood cognitive ability, education and occupational social class. Our findings confirm the need for further research on the association between diet and cognition from a life-course perspective.

Adherence to a Dietary Approaches to Stop Hypertension (DASH)-type diet over the life course and associated vascular function: a study based on the MRC 1946 British birth cohort.

Little is known about long-term associations between the Dietary Approaches to Stop Hypertension (DASH) diet and conventional cardiovascular (CV)-risk factors as well as novel measures of vascular function. This study aimed to examine whether long-term adherence to a DASH-type diet in a British birth cohort is associated with conventional CV-risk factors and two vascular function markers, carotid intima-media thickness (cIMT) and pulse wave velocity (PWV). Data came from 1409 participants of the Medical Research Council (MRC) National Survey of Health and Development. Dietary intake was assessed at 36, 43, 53 and 60-64 years using 5-d estimated food diaries. The DASH-type diet score was calculated using the Fung index. Conventional CV-risk factors (blood pressure (BP) and lipids), cIMT in the right and/or left common carotid artery and PWV was measured when participants were 60-64 years. Associations between the DASH-type diet score and outcomes were assessed using multiple regression models adjusted for socioeconomic position, BMI, smoking and physical activity. Participants in higher sex-specific quintiles (Q) of the long-term DASH-type diet had lower BP (P≤0·08), higher HDL-cholesterol (P<0·001) and lower TAG (P<0·001) compared with people in Q1. Participants in Q5 of the long-term DASH-type diet had lower PWV (-0·28 sd; 95 % CI -0·50, -0·07, P trend=0·01) and cIMT (-0·24 sd; 95 % CI -0·44, -0·04, P trend=0·02) compared with participants in the Q1. This association was independent of the conventional CV-risk factors. Greater adherence to a DASH diet over the life course is associated with conventional CV-risk factors and independently associated with cIMT and PWV.

Irregularity of energy intake at meals: prospective associations with the metabolic syndrome in adults of the 1946 British birth cohort.

Irregularity in eating patterns could be a potential cardiometabolic risk factor. We aimed to study the associations of irregular intake of energy at meals in relation to cardiometabolic risk factors 10 and 17 years later. Variability of energy intake data - derived from 5-d estimated diet diaries of cohort members of the National Survey for Health and Development collected at ages 36 (n 1416), 43 (n 1505) and 53 years (n 1381) - was used as a measure for irregularity. Associations between meal irregularity scores with cardiometabolic risk factors measured 10 and 17 years later were investigated using linear mixed models and logistic regression models. The results showed that irregularity scores changed significantly over the years (P<0·05). At age 36 years, subjects with a more irregular intake of energy at lunch (OR 1·42; 95 % CI 1·05, 1·91) and between meals (OR 1·35; 95 % CI 1·01, 1·82) had an increased risk for the metabolic syndrome 17 years later; at lunch was also associated with an increased waist circumference (OR 1·58; 95 % 1·27, 1·96) and TAG levels (OR 1·33; 95 % CI 1·02, 1·72). At age 43 years, subjects with a more irregular intake at breakfast had an increased risk of the metabolic syndrome 10 years later (OR 1·53; 95 % CI 1·15, 2·04), as well as an increased BMI (OR 1·66; 95 % CI 1·31, 2·10), waist circumference (OR 1·53; 95 % CI 1·23, 1·90) and diastolic blood pressure (OR 1·42; 95 % CI 1·13, 1·78). In conclusion, subjects with a more irregular intake of energy, mostly at breakfast and lunch, appeared to have an increased cardiometabolic risk 10 and 17 years later.

A high-fat, high-glycaemic index, low-fibre dietary pattern is prospectively associated with type 2 diabetes in a British birth cohort.

The combined association of dietary fat, glycaemic index (GI) and fibre with type 2 diabetes has rarely been investigated. The objective was to examine the relationship between a high-fat, high-GI, low-fibre dietary pattern across adult life and type 2 diabetes risk using reduced rank regression. Data were from the MRC National Survey of Health and Development. Repeated measures of dietary intake estimated using 5-d diet diaries were available at the age of 36, 43 and 53 years for 1180 study members. Associations between dietary pattern scores at each age, as well as longitudinal changes in dietary pattern z-scores, and type 2 diabetes incidence (n 106) from 53 to 60-64 years were analysed. The high-fat, high-GI, low-fibre dietary pattern was characterised by low intakes of fruit, vegetables, low-fat dairy products and whole-grain cereals, and high intakes of white bread, fried potatoes, processed meat and animal fats. There was an increasing trend in OR for type 2 diabetes with increasing quintile of dietary pattern z-scores at the age of 43 years among women but not among men. Women in the highest z-score quintile at the age of 43 years had an OR for type 2 diabetes of 5·45 (95 % CI 2·01, 14·79). Long-term increases in this dietary pattern, independently of BMI and waist circumference, were also detrimental among women: for each 1 sd unit increase in dietary pattern z-score between 36 and 53 years, the OR for type 2 diabetes was 1·67 (95 % CI 1·20, 2·43) independently of changes in BMI and waist circumference in the same periods. A high-fat, high-GI, low-fibre dietary pattern was associated with increased type 2 diabetes risk in middle-aged British women but not in men.

Diurnal eating rhythms: association with long-term development of diabetes in the 1946 British birth cohort.

BACKGROUND AND AIMS: Few studies have described the association between time-of-day of macronutrient intake and diabetes. This study examined the prospective association between time-of-day and nutrient composition of eating occasions in relation to diabetes incidence in the 1946 British birth cohort. METHODS AND RESULTS: The study included 1618 survey members who completed dietary assessment at age 43 (1989) and for whom data on glycosylated haemoglobin at age 53 years (1999) were available. Diet was assessed using 5d estimated diaries, divided into seven meal slots: breakfast, mid-morning, lunch, mid-afternoon, dinner, late evening and extras. Diabetes was defined by glycosylated haemoglobin (HbA1c) ≥ 6.5% or diabetes medication use. The association between time-of-day of macronutrient intake at age 43 years and diabetes at age 53 years was assessed using logistic multivariate nutrient density models after adjustment for potential confounders. There were 66 cases of diabetes at age 53 years. Survey members with diabetes obtained 50.4% of their energy from carbohydrate at breakfast compared to 55.9% in survey members without diabetes (P = 0.001). Increasing carbohydrate intake at breakfast at the expense of fat was related to lower odds ratio (OR) of diabetes (OR = 0.86; 95%CI = 0.79-0.93; P < 0.001). This relationship was attenuated after adjustment for body mass index and waist circumference. CONCLUSION: Increasing energy intake from carbohydrate at the expense of fat at breakfast is inversely associated with 10-year diabetes incidence. However, further studies are required to elucidate whether the type or source of carbohydrates or fat influences the above association.

Amyloid ß influences the relationship between cortical thickness and vascular load.

INTRODUCTION: Cortical thickness has been proposed as a biomarker of Alzheimer's disease (AD)- related neurodegeneration, but the nature of its relationship with amyloid beta (Aß) deposition and white matter hyperintensity volume (WMHV) in cognitively normal adults is unclear. METHODS: We investigated the influences of Aß status (negative/positive) and WMHV on cortical thickness in 408 cognitively normal adults aged 69.2 to 71.9 years who underwent 18F-Florbetapir positron emission tomography (PET) and structural magnetic resonance imaging (MRI). Two previously defined Alzheimer's disease (AD) cortical signature regions and the major cortical lobes were selected as regions of interest (ROIs) for cortical thickness. RESULTS: Higher WMHV, but not Aß status, predicted lower cortical thickness across all participants, in all ROIs. Conversely, when Aß-positive participants were considered alone, higher WMHV predicted higher cortical thickness in a temporal AD-signature region. DISCUSSION: WMHV may differentially influence cortical thickness depending on the presence or absence of Aß, potentially reflecting different pathological mechanisms.