Kelsey Matichuk, RMT

04/26/2026

04/23/2026

The "no coffee after 2pm" rule isn't a rule. It's an average. And averages lie about metabolism.
Caffeine is cleared almost entirely by a single liver enzyme, CYP1A2. Activity of that enzyme varies 15 to 40-fold across healthy adults.

Grzegorzewski and colleagues (2022, Front Pharmacol) ran a systematic pharmacokinetic analysis across 141 published studies and documented substantial inter-individual variability in caffeine elimination half-life, ranging from roughly 2 hours at the fast end to 10 hours or more at the slow end. A 4 to 5-fold spread in how long a single dose stays active.

The variability has both genetic and environmental drivers. Polymorphisms in the CYP1A2 gene contribute, though their practical effect depends heavily on whether the enzyme is being induced. Sachse and colleagues (1999, Br J Clin Pharmacol) showed that the CYP1A2 -163C>A polymorphism (later called *1F) was associated with differential inducibility in smokers but not in non-smokers. Genotype alone explains a modest fraction of the total variance.

Environment shifts the range more dramatically. Smoking induces CYP1A2 and can cut caffeine half-life by 30 to 50%. Oral contraceptive pills inhibit CYP1A2 and roughly double it. Third-trimester pregnancy can triple it, pushing half-life past 15 hours. Same gene, dramatically different kinetics depending on physiological state.

What this means for the clock. A 200mg coffee at 2pm follows two very different trajectories. At the fast end of the range (half-life around 3 hours), plasma caffeine drops to trace levels before 10pm bedtime. At the slow end (half-life around 8 hours), roughly half the peak dose is still circulating at bedtime and a meaningful fraction remains active through the night.

Drake and colleagues (2013, J Clin Sleep Med) gave 400mg of caffeine at bedtime, 3 hours before bed, and 6 hours before bed in healthy adults. All three conditions reduced sleep compared to placebo, including the 6-hour condition. The study didn't stratify by CYP1A2 activity, but the signal that 6 hours before bed still disrupts sleep in an unselected population tells you the population average doesn't leave much margin. For slower metabolizers, the window gets longer.

The real answer is individual. If caffeine consistently disrupts your sleep even with early cutoffs, you are likely on the slower end of the distribution. If you sleep fine after 4pm coffee, you are likely on the faster end. The clock rule was always a population average. Your actual cutoff is a half-life, not a time of day.

Grzegorzewski et al., Front Pharmacol, 2022
Sachse et al., Br J Clin Pharmacol, 1999
Drake et al., J Clin Sleep Med, 2013

04/22/2026

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04/22/2026

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A nine-month-old baby—often referred to as “KJ”—became part of a groundbreaking medical milestone: doctors used CRISPR to directly correct a genetic error inside his body.
The problem was incredibly small—but devastating. One “letter” mistake in billions of DNA pairs meant his liver couldn’t properly process ammonia, a toxic byproduct. Each time he ate, dangerous levels could build up in his blood and threaten his brain. Traditional treatments can manage this kind of condition, but they don’t fix the root cause.
So doctors tried something new.
Using CRISPR, they designed a personalized therapy aimed specifically at that single faulty gene. Think of it less like rewriting an entire book and more like correcting one critical typo. The treatment was tailored to him alone, delivered into his bloodstream, and targeted to his liver cells—where the problem existed.
The result? Early reports showed the therapy working. His body began handling ammonia more effectively, and he started hitting developmental milestones that once seemed out of reach.
It’s important to understand: this isn’t a routine cure yet. It’s an early, highly experimental step in a field that’s still developing. But it signals something huge—medicine moving from treating symptoms to fixing problems at their genetic source.
One patient. One targeted edit. A glimpse of what future healthcare might look like.

04/22/2026

04/22/2026

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Calli Hauger-Thackery, representing Great Britain, is currently 22 weeks pregnant and expecting her first child, a baby boy, at the end of August!

Despite this, she competed in the Boston Marathon on Monday, finishing 65th with an impressive time of 2:43:58 🤯

04/20/2026

Vision loss from age-related macular degeneration and inherited retinal dystrophies shares a common biological culprit: the death of retinal pigment epithelium (RPE) cells — the single-cell monolayer that nourishes and maintains the photoreceptors of the central retina. Once RPE cells are lost, photoreceptors follow, and with them, central vision. 👁️ A 2025 Phase I/II trial from the National Eye Institute in collaboration with the Foundation Fighting Blindness reported that surgical transplantation of a bioengineered RPE monolayer — grown from human embryonic stem cells on an ultrathin biodegradable scaffold and delivered beneath the retina via a specialized syringe system — restored measurable visual function in 8 of 12 patients with advanced dry age-related macular degeneration who were functionally blind at baseline.

The manufactured RPE patch closely replicates the structural and functional properties of native RPE: it demonstrates phagocytosis of photoreceptor outer segments, supports photoreceptor metabolic exchange, and maintains barrier function — the three critical activities that keep photoreceptors alive. 🔬 Six months post-transplant, 7 patients showed rescue of preexisting photoreceptors adjacent to the transplant site on optical coherence tomography, and visual acuity improvements ranged from 7 to 17 ETDRS letters — clinically meaningful gains in a population for whom no other disease-modifying treatment exists.

The scaffold dissolves within 90 days, leaving behind a stable RPE monolayer integrated with the native retinal tissue and — critically — not rejected by the immune-privileged eye environment. 💊 The team is now refining a next-generation iPSC-derived RPE patch using the patient's own cells to eliminate even the minimal immunosuppression currently required.

Science is learning to paint light back into eyes that had gone dark. 🌍

Source: National Eye Institute & Foundation Fighting Blindness, Nature Biotechnology, 2025