N° 99 | April 2015

Education and WHO Recommendations for Fruit and Vegetable Intake Are Associated with Better Cognitive Function in a Disadvantaged Brazilian Elderly Population: A Population-Based Cross-Sectional Study

Due to increased longevity worldwide, cognitive decline and dementia are increasing exponentially1. Evidence suggests that age-dependent accumulation of mtDN2 leads to the production of free radical species (ROS), resulting in mitochondrial and synaptic damage in neurons which is present from the early stages of Alzheimer disease (AD)3. Fruit and vegetables are rich in antioxidant micronutrients, which have anti-inflammatory properties and can scavenge free radicals offering neuron-protection4,5 These properties might have the potential to delay cognitive decline and prevent progression to dementia.

Epidemiological studies suggest a positive association between the intake of fruit and vegetables and decreased risk of cognitive impairment or dementia, but little is known about the optimal amount of fruit and vegetables associated with a lower risk of cognitive impairment. In 2004, the WHO launched a strategy to reduce the prevalence of non-communicable diseases. This strategy included recommendations of five or more servings of fruit and/or vegetables a day (400 g/day)6. However, no studies have examined whether the WHO recommendations offer protection against cognitive impairment. Apart from genetic factors, social determinants of mental health are associated with increased risk of cognitive decline and dementia7, such as income, education and healthy lifestyles including physical activity8,9,10.

Brazil has one of the fastest-aging populations in the world, with the prevalence of dementia ranging from 5 (1%) to 8 (8%)1. This study11 examined the relationship between cognitive impairment and daily intake of fruit and vegetables, including ¨five a day¨ WHO recommendations, in Brazilian elderly participants from the Sao Paulo Ageing and Health Study (SPAH study). The relationship between cognitive impairment and factors such as years of education, physical activity, APOE gene, co-morbidities and lifestyle variables was also assessed.

The SPAH study

The SPAH study is a cross-sectional population-based study carried out with elderly participants ≥ 65 years of age from census sectors which represented the lowest Human Development Indexes in Brazil at the time. Eligible participants were recruited through door-knocking of all households within the census sector boundaries. Institutionalized individuals and those with a dementia diagnosis at entry (n= 105), were not included. A total of 2,072 agreed to participate - a response rate of 91.4%. The assessment of cognitive function was carried out using the protocol developed by the 10/66 Dementia Research Group for use in population-based and validated in elderly Brazilians12,13. To assess the fruit and vegetable intake, the corresponding section of a Brazilian Food Frequency Questionnaire (FFQ) was used14. A detailed description of the whole protocol has been published previously11.

Key findings and plausible explanations

The results of the SPAH study suggested a protective role for those meeting WHO recommendations against cognitive impairment. In fact, for daily intakes of fruit and vegetables ≥ 400 grams/day there was a 47% decreased prevalence of cognitive impairment. Moreover, within the group of those with one or more years of education compared to no education (illiteracy), to be physically active compared to sedentary or to have HDLcholesterol levels above 50 mg/dl compared to levels ≤ 50 mg/dl strongly decreased the prevalence of cognitive impairment. This study found the important interaction between decreased prevalence of cognitive impairment and both years of education and physical activity, and between years of education and increased HDL-cholesterol levels, confirming the importance of social determinants in healthier choices and better quality of life in this elderly population. Even though the population presented very low levels of years of education, those with one or more years showed a strong decrease of prevalence of cognitive impairment. Although education is not directly related to the neuropathologic lesions in dementia, studies suggest that it may reduce the impact of such lesions by increasing the cognitive reserve and by shaping food choices8. Recent evidence demonstrates that literacy and the first years of education are associated with remarkable changes in cortical network organization and function15.

Translation to public health guidance

These findings support recommendations to increase F&V intake at least to meet WHO recommendations. The present results show that promoting education and health policies to encourage and enable healthy lifestyles in disadvantaged populations could make a significant difference. A more comprehensive understanding of the social determinants of mental health is needed to develop effective public policies to prevent or delay age associated cognitive impairment.

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