The use of the Chinese study about healthy aging for elderly Chinese people is egregiously misleading. The OP uses it to make three separate points, about cognitive impairment, dose-response effects and lower overall odds of healthy aging. But it’s pretty clear that the study is basically showing the effects of poverty on health in old age!
Elderly Chinese people are mostly vegetarian or vegan because a) they can’t afford meat, or b) have stopped eating meat because they struggle with other health issues, both of which would massively bias the outcomes! So their poor outcomes might be partly through diet-related effects, like nutrient/protein deficiency, but could also be sanitation, malnutrition in earlier life (these are people brought up in extreme famines), education (particularly for the cognitive impairment test), and the health issues that cause them to reduce meat. The study fails to control for extreme poverty by grouping together everyone who earned <8000 Yuan a year (80% of the survey sample!), which is pretty ridiculous, because the original dataset should have continuous data.
But, the paper does control for diet quality, and it also makes it abundantly clear that diet quality is the real driver, and that healthy plant-based diets score similarly to omnivorous diets! “With vegetarians of higher diet quality not significantly differing in terms of overall healthy aging and individual outcomes when compared to omnivores”.
Probably less importantly, it conditions on survival to 80, which creates a case of survivorship bias/collider bias. So there could be a story where less healthy omnivores tend to die earlier, and the survivors appear healthier.
The use of the Chinese study about healthy aging for elderly Chinese people is egregiously misleading. The OP uses it to make three separate points, about cognitive impairment, dose-response effects and lower overall odds of healthy aging. But it’s pretty clear that the study is basically showing the effects of poverty on health in old age!
Elderly Chinese people are mostly vegetarian or vegan because a) they can’t afford meat, or b) have stopped eating meat because they struggle with other health issues, both of which would massively bias the outcomes! So their poor outcomes might be partly through diet-related effects, like nutrient/protein deficiency, but could also be sanitation, malnutrition in earlier life (these are people brought up in extreme famines), education (particularly for the cognitive impairment test), and the health issues that cause them to reduce meat. The study fails to control for extreme poverty by grouping together everyone who earned <8000 Yuan a year (80% of the survey sample!), which is pretty ridiculous, because the original dataset should have continuous data.
But, the paper does control for diet quality, and it also makes it abundantly clear that diet quality is the real driver, and that healthy plant-based diets score similarly to omnivorous diets! “With vegetarians of higher diet quality not significantly differing in terms of overall healthy aging and individual outcomes when compared to omnivores”.
Probably less importantly, it conditions on survival to 80, which creates a case of survivorship bias/collider bias. So there could be a story where less healthy omnivores tend to die earlier, and the survivors appear healthier.