Can someone tl;dr? Not that the paper is too long, but I think I'd need to go back to university and major in biology or statistics to understand what they discovered and more importantly what it might mean.
When you have TC > 200 mg/dL - each 1mmol/L increases mortality.
The confidence interval was high.
> In the age groups of 18–34, 35–44, 45–54, 55–64, 65–74, and 75–99 years, each 1 mmol/L higher TC increased mortality by 14%, 13%, 8%, 7%, 6%, and 3%, respectively (P < 0.001 for each age group), for TC ≥ 200 mg/dL, while the corresponding TC changes decreased mortality by 13%, 27%, 34%, 31%, 20%, and 13%, respectively, in the range < 200 mg/dL (P < 0.001 for each age group). TC had U-curve associations with mortality in each age-sex group. TC levels associated with lowest mortality were 210–249 mg/dL, except for men aged 18–34 years (180–219 mg/dL) and women aged 18–34 years (160–199 mg/dL) and 35–44 years (180–219 mg/dL). The inverse associations for TC < 200 mg/dL were stronger than the positive associations in the upper range.
I know of someone with TC around 240 and the doctor didn't prescribe statins. Not a medical advice.
This is why the HDL to triglycerides ratio exists.
https://www.nature.com/articles/s41598-018-38461-y/figures/2
230 mg/dL is associated with the lowest mortality, and anything below or above that increases mortality.
Implies a causal relationship. In reality, it's much more likely that causality points the other way, and an underlying disease like cancer is causing low cholesterol: https://www.ahajournals.org/doi/10.1161/01.cir.92.9.2396
Meaning: lower cholesterol is not always correlated with lower mortality.