Dietary patterns in the older New Zealand adult and their associations with cognitive function and metabolic syndrome : the Researching Eating, Activity, and Cognitive Health (REACH) study : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Albany, New Zealand
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Date
2021
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Massey University
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Abstract
Background: The global population is ageing. Ageing and poor diet are common risk factors for cognitive decline and metabolic syndrome which reduce functionality in later years. A dietary pattern approach considers the full complexity of the diet. Dietary patterns in an older New Zealand context have not been identified nor their associations with cognitive function or metabolic syndrome.
Aims and objectives: This thesis, referred to as the REACH (Researching, Eating, Activity, and Cognitive Health) study, explored associations between dietary patterns and cognitive function and metabolic syndrome in older New Zealand adults. To achieve the aim a food frequency questionnaire (FFQ) was assessed for reproducibility, relative validity, and its suitability to derive robust dietary patterns. Further, associations between these dietary patterns and their nutrient and energy intake; the socio-demographic and lifestyle factors of the participants; and cognitive function and metabolic syndrome outcomes were examined.
Method: Community-dwelling adults from Auckland, New Zealand were recruited (aged 65-74 years, 36% male, n 371). Dietary patterns were derived from a 109-item FFQ using 57 food groups and principal component analysis. Nutrient, energy, and alcohol intake were calculated using FOODfiles, the New Zealand Food composition database.
The REACH FFQ and its derived dietary patterns were assessed for reproducibility and relative validity in a sub-set of the REACH participants (n 294). Reproducibility was assessed using an identical FFQ (FFQ2) administered one month after the initial REACH FFQ. A 4-day food record (4-DFR), collected between FFQ administrations, assessed relative validity.
Cognitive function, covering six domains (global cognition, attention and vigilance, executive function, episodic memory, working memory and spatial memory), was assessed using COMPASS (Computerised Mental Performance Assessment System). Self-administered questionnaires collected health (medication and supplement intake), demographic and lifestyle [including sex, education levels, living status (alone or with someone), smoking status, physical activity levels, address (for Index of Multiple Deprivation)], and physical activity (International Physical Activity Questionnaire) data. A fasted blood sample was collected for measuring genetic [Apolipoprotein E -ε4 (APOE -ε4)] and biochemical markers (triglycerides, high- and low-density lipoprotein cholesterol). Blood pressure and anthropometric measures [weight, height, waist circumference, and body fat % (using dual X-ray absorptiometry)] were collected. Metabolic syndrome was defined by the National Cholesterol Education Program Adult Treatment Panel III.
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Statistical analyses performed: Reproducibility and relative validity of the REACH FFQ (food group intakes) and its derived dietary patterns (scores) were assessed using Spearman correlation coefficients (acceptable correlation rho=0.20-0.49), weighted kappa statistic (κw) (acceptable statistic κw=0.20-0.60), and Bland-Altman analysis including mean difference, limits of agreement, plots, and slope of bias. The similarity between dietary pattern loadings were assessed using Tucker’s congruence coefficient.
Linear or logistic regression were used to examine associations between dietary patterns and their nutrients; socio-demographic and lifestyle factors; and health outcomes. Confounding adjustments included age, sex, education, index of multiple deprivation, energy intake, APOE -ε4, and physical activity.
Results: In the validation study, the FFQ food groups showed good reproducibility (mean correlation coefficient = 0.69, mean κw = 0.62) and acceptable relative validity (mean correlation coefficient = 0.45, mean κw = 0.38) though Bland Altman plots showed bias and mean differences significantly different to zero in some food groups. Three similar dietary patterns were identified from each dietary assessment tool: ‘Mediterranean style’, ‘Western’, and ‘prudent’. Congruence coefficients between factor loadings ranged from 0.54 to 0.80. Correlations of dietary pattern scores ranged from 0.47 to 0.59 (reproducibility) and 0.33 to 0.43 (validity) (all P<0.001); weighted kappa scores from 0.40 to 0.48 (reproducibility) and 0.27 to 0.37 (validity); limits of agreement from ± 1.79 to ± 2.09 (reproducibility) and ± 2.09 to ± 2.27 (validity); a slope of bias was seen in the ‘prudent’ pattern for reproducibility and validity (P<0.001).
From the full REACH dietary data set, three valid dietary patterns were derived explaining 18% of the variation in the diet. The ‘Mediterranean style’ pattern (salad vegetables; leafy cruciferous vegetables; other vegetables; avocados and olives; alliums; nuts and seeds; white fish and shellfish; oily fish; berries; water; salad dressings; cruciferous vegetables; eggs; cheese; tomatoes; and all other fruit) was associated with higher levels of beta-carotene equivalents, vitamin E, and folate intake (all P<0.001, all R2 ≥ 0.26), along with being female, having a higher physical activity level, and higher education (P<0.001, R2 = 0.07). The ‘Western’ pattern (processed meat; sauces and condiments; cakes, biscuits and puddings; meat pies and chips; processed fish; confectionery; vegetable oils; beer; chocolate; salad dressings; cheese; and sweetened cereal) was associated with higher daily energy intake (P<0.001, R2 = 0.43), along with being male, having a higher alcohol intake, living with others, and a secondary education (males only) (P<0.001, R2 = 0.16). The ‘prudent’ pattern (dried legumes; soy-based foods; fresh and frozen legumes; whole grains; carrots; and
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spices) was associated with a higher fibre and carbohydrate intake (both P<0.001, both R2 ≥ 0.25), along with higher physical activity and lower alcohol intake (P<0.001, R2 = 0.15).
Neither the ‘Mediterranean style’ nor ‘prudent’ patterns were associated with either cognitive function or metabolic syndrome. The ‘Western’ pattern was not associated with cognitive function, but was positively associated with metabolic syndrome [odds ratio = 1 .67 (95% CI 1.08, 2.63)] (P=0.02).
Being younger (P<0.05), female (P<0.001), having a higher education (P<0.01) or no APOE -ε4 allele (P<0.05) were associated with better cognitive function. Higher deprivation (P<0.001) was associated with metabolic syndrome.
Conclusion: A novel and robust study with valid tools did not find any associations between dietary patterns and cognitive function in older adults living in New Zealand. Age, sex, education, and the APOE -ε4 allele were more predictive of cognitive function than the dietary patterns.
A ‘Western’ dietary pattern and higher deprivation were predictive of metabolic syndrome. To reduce the odds of metabolic syndrome, actions should aim to improve deprivation, and shift people’s dietary intake away from the ‘Western’ dietary pattern.
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Cognition disorders, Diet, Metabolism, Disorders, Older people, Nutrition, New Zealand