Background: Systemic inflammation is known as a risk factor of cognitive decline. Objective: To investigate the effects of propolis on cognitive decline and systemic inflammation in elderly people living at high altitude. Methods: Sixty participants (average 72.8 years) living at altitude (2,260 meters) were randomized to receive propolis (0.83g, n=30) or placebo (n=30) for 24 months. Cognitive outcomes were assessed using MMSE and serum cytokine levels were measured for 24 months in a double-blind study. Results: MMSE scores were 26.17 at baseline and 23.87 at 24 months in placebo group. Compared to placebo group, improvements of MMSE scores were significant in propolis-treated subjects (p=0.007) with a response emerging over time (time points×group interaction, p=0.016). In addition, the serum IL-1β and IL-6 levels were significantly different across treatments (p<0.0001) showing upward and downward trends in placebo- and propolis-treated subjects, respectively (p<0.0001). Serum levels of TNF-α were not significantly different across treatment (p=0.0528) but with a response emerging over time (time points×group interaction, p=0.016). In contrast, serum levels of TGFβ1 were significantly different across treatments (p<0.0001) showing downward and upward trends in placebo- and propolis-treated subjects, respectively. Serum levels of IL-10 were significant for the effect of groups (p=0.0411). Furthermore, MMSE scores correlated with the decrease in IL-1β and the increase in TGFβ1 in serum. Conclusion: Elderly people living at high altitude developed to MCI in 24 months with exacerbation of systemic inflammation. Ingestion of propolis (>12 months) protected against cognitive decline after systemic inflammation was reduced.
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