Dampened inflammation and reduced risk of osteoarthritis among non-industrialized societies

Objectives: Anthropological research suggests that people in non-industrialized societies (hunter-gatherers, subsistence farmers, pastoralists) are at lower risk of osteoarthritis than people in industrialized societies. Here, we propose that this may be due to people in non-industrialized societies having dampened inflammatory activity, a key factor in osteoarthritis pathogenesis. Design: This narrative review focuses on evidence that four environmental variables common among non-industrialized societies contribute to dampening inflammatory activity and thus potentially lowering OA risk: low levels of adiposity, high physical activity levels, diets consisting of minimally processed foods, and infections from helminths. Results: Although people in non-industrialized societies experience intermittent, pathogen-induced spikes in inflammation, they do not typically experience the chronic, low-grade pattern of inflammation implicated in osteoarthritis pathogenesis. Excess adipose tissue is well documented to be a potent source of pro-inflammatory mediators involved in osteoarthritis pathogenesis; thus, the rarity of obesity among non-industrialized societies is likely a major reason for any reduced osteoarthritis risk. Physical activity and diet among non-industrialized societies have the potential to curb inflammation and osteoarthritis through several mechanistic pathways, yet the relative importance of each pathway has yet to be fully resolved. A role for helminths in dampening inflammation and lowering OA risk is theoretically plausible but speculative based on current evidence. Conclusions: More research among non-industrialized societies will be required to rigorously investigate the links proposed here between industrialization, inflammation, and risk of osteoarthritis. Opportunities to do so are disappearing, as lifestyles among such societies are rapidly changing.