Dietary flavonoids and cognitive impairment in Chinese older adults

Introduction: Cognitive impairment (CI) in older adults refers to impairment in cognition function beyond normal aging. Previous studies have reported the effect of dietary antioxidants, especially flavonoids on cognitive function in older adults, suggesting that high dietary flavonoids intake may reduce the risk of cognitive impairment. However, most of these studies were reported in Caucasian older populations in Western countries. Moreover, some studies were positive, which others were negative studies. There was no previous study regarding dietary flavonoids and cognitive impairment among Chinese older adults. Objectives: The objectives of this study were to explore the association between dietary intake flavonoids and the risk of cognitive impairment in Chinese older adults, and to identify the independent factors associated with the risk of cognitive impairment in Chinese older adults. Method: This study was a retrospective cross-sectional study, 200 patients who fulfilled the inclusion and exclusion criteria and gave written informed consent were recruited from the Geriatric clinics in Queen Mary Hospital, Hong Kong, from 11th July to 31st October 2011. All recruited subjects were invited to attend face-to-face interviews. Brief cognitive assessments by the Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were done for all subjects. Every subject also answered a detailed questionnaire on socio-demographic, type and frequency of diet items (food frequency questionnaire) and co-morbid diseases. Main outcome measure: The primary outcome measure was cognitive function, using an education-adjusted MMSE cut-off s to categorize the subjects into two groups (i.e. normal cognitive group and cognitively impaired group). Results: 200 subjects were recruited, 104 participants (37 males and 67 females) were in the normal cognitive group and 96 subjects (22 males and 74 females) were in the cognitively impaired group. The mean amount of dietary flavonoids intake of the cognitively normal group was higher than that of the cognitively impaired group (i.e. 291.84 grams/day and 240.92 grams/day respectively; p=0.006 Mann-Whitney U test). Other common dietary nutrients were also compared between the two groups. The dietary carbohydrate (p<0.001), total sugar (p<0.001), vitamin C (p=0.001) and folic acid (p<0.001) intakes were significantly related to cognitive impairment (using chi-square statistics). After adjustment for age, gender, education, exercise pattern, the dietary flavonoids intake was not independently associated with cognitive impairment. However, after adjustment for age, education level, exercise pattern and BMI, the higher to highest quartile of dietary carbohydrate intake (184.184-1176.703g/d), high total sugar intake (0.166-35.102g/d), highest quartile of vitamin C intake (139.803-900.952mg/d), the third and fourth quartiles of folic acid intake (208.899-1544.418mcg/d) were significantly associated with reduced risks of cognitive impairment. Older adults who had regular exercise (both less and more than 30 minutes per day) had lower risk of cognitive impairment than those who never did exercise (OR= 0.361, 95% confidence interval=0.167-0.784 for less than 30 minutes/d; OR=0.137, 95% confidence interval=0.048-0.396 for more than 30 minutes/d). We also found high BMI was associated with a reduced risk of cognitive impairment with an OR of 0.897 (95% confidence interval=0.816-0.987). Besides, the increasing age was also associated with cognitive impairment (OR=1.059, 95% confidence interval=1.007-1.115). Conclusion: In summary, the present study demonstrated that the dietary flavonoids intake was not significantly associated with the risk of cognitive impairment in Chinese older adults in Hong Kong.

並列關鍵字

Cognition disorders in old age ； Flavonoids

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