Cholesterol Levels and Risk of Death: Insights from Large Studies in Korea and the US

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High or low cholesterol is often discussed in health news, but what does it really mean for your overall risk of dying? Two large studies—one from Korea and one from the US—looked at how cholesterol levels relate to “all-cause mortality,” which simply means death from any reason, including heart disease, cancer, accidents, or other illnesses. (These studies didn’t specifically focus on dementia or Alzheimer’s disease, but since all-cause mortality includes deaths from those conditions, any broad patterns might indirectly touch on them. However, neither study analyzed or found direct links between cholesterol levels and dementia risk— their main goal was to explore overall survival patterns based on cholesterol.)

Key Similarities in the Findings

Both studies followed huge groups of adults over many years and found a “U-shaped” relationship between cholesterol and death risk. In plain terms, this means:

– Very low cholesterol was linked to a higher chance of dying.

– Moderately high cholesterol (not extremely high) seemed protective, with the lowest death risks in certain “sweet spot” ranges.

– Very high cholesterol

also raised the risk, though less dramatically in some groups. This U-shape held true across ages and sexes, but the ideal cholesterol range varied slightly by age, sex, and the type of cholesterol measured. The researchers adjusted their results for other factors like age, smoking, blood pressure, diabetes, and body weight to make the connections clearer. Importantly, these are observational studies, so they show associations, not direct cause-and-effect (e.g., low cholesterol might be a sign of underlying health issues rather than the cause of higher mortality).

The Korean Study: Total Cholesterol in Over 12 Million People

This research tracked about 12.8 million Korean adults (ages 18–99) for an average of 10.5 years, using health data from national checkups. During this time, around 694,000 people died. They measured “total cholesterol” (TC), which includes all types of cholesterol in your blood.

  • Main Results: The safest TC range for lowest death risk was generally 210–249 mg/dL for most adults. For younger folks (18–44 years), it was a bit lower (160–219 mg/dL, depending on sex). Below 200 mg/dL, every 39 mg/dL increase in TC was tied to 23% lower mortality risk. Above 200 mg/dL, the same increase linked to 7% higher risk.
  • By Age and Sex: The U-shape was consistent, but the risks from low cholesterol were stronger in middle-aged people (45–64), while high cholesterol risks were more pronounced in younger adults.
  • Dementia Angle: No specific mention or analysis of dementia or Alzheimer’s risk—the focus was purely on overall deaths.

The US Study: LDL Cholesterol in Nearly 20,000 People

This one used data from a national US health survey (NHANES) from 1999–2014, following 19,034 adults (average age 46) for about 8 years on average. About 1,600 deaths occurred (after excluding early deaths to avoid bias). They focused on “LDL cholesterol” (LDL-C), often called “bad cholesterol” because high levels can build up in arteries.

  • Main Results: People with very low LDL-C (under 70 mg/dL) had a 37% higher risk of dying compared to those in the 100–129 mg/dL range. The U-shape showed higher risks at both extremes. Similar patterns appeared for heart-related deaths.
  • By Groups: The link held across subgroups like race, smoking status, and health conditions (e.g., stronger in non-Hispanic Whites or former smokers).
  • Dementia Angle: Alzheimer’s was listed as one possible cause in the all-cause mortality data, but the study didn’t break it down or find any specific connection to LDL-C levels. No mention of cognitive decline.

What Does This Mean for Everyday People?

If your cholesterol is too low or too high, it might signal broader health risks, but the “optimal” level could depend on your age and sex. For example, younger people might benefit from slightly lower levels, while older adults see lower risks with moderately higher ones. These findings challenge the idea that lower cholesterol is always better—sometimes very low levels (possibly from poor nutrition, illness, or medications) could be a red flag.

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