Siim Land

How does immune aging differ in people who live past 100?

Typical aging: fewer new T cells, weaker responses to unfamiliar infections, and more chronic inflammation.

Exceptional longevity: centenarians show signs that their immune systems have adapted in three ways:

1. Their T and B cells remember past threats better
2. Natural killer cells and certain T cells maintain the ability to kill infected or abnormal cells.
3. They can regulate inflammation - dial it up and downregulate as needed

PMID: 42794847

AMINO ACID CHEAT SHEET:
- Arginine: wound healing + nitric oxide production
- Cysteine: antioxidant defense + detoxification support
- Citrulline: blood flow + ammonia clearance
- Glycine: collagen/glutathione + better sleep quality
- Glutamine: gut/mucosa + immune support
- Leucine: protein synthesis + muscle
- Methionine: protein synthesis + methylation support
- Proline: collagen + joint/tissue repair
- Tryptophan: neurotransmitters + sleep support

8 runners ran ~118 marathons over 140 days (~6 per week). They got CT scans before and after.

- 4 of them with 0 baseline plaque saw no progression after the event
- In the 4 with pre-existing plaque, plaque volume increased by 4.8, 16.9, 17.3, and 94.0 mm³

Lifelong runners often see more plaque in their arteries, but there's important nuance to this: youtu.be/wL9cMhqFHJs

PMID: 28683972

Training one arm can help prevent muscle loss in the other.

In a 3-week study, men had one arm immobilized in a cast. Biceps muscle size in that arm decreased by 12% with no training. It stayed roughly unchanged in men who did curls with the other arm.

PMID: 36849120

Deep sleep can decline earlier than you might expect.

A study on 149 healthy men found that deep sleep averaged ~19% of total sleep at ages 16–25 and 3.4% at ages 36–50.

The middle-aged group spent more of the night in lighter sleep.

Full video on declining deep sleep: youtu.be/lPfEk9Kvf-4

PMID: 10938176