Why is my HRV down lately?

Your HRV (RMSSD) has fallen about 11% over the last 90 days, from a 65 ms baseline to 58 ms today. Three things in your data line up with that drop, in order of likely impact: 1. Iron status. Your most recent Iron panel · 2026-04-12 shows ferritin at 14 ng/mL — well below the 30 ng/mL floor. Iron deficiency throttles parasympathetic tone before it ever shows up as low hemoglobin, which is exactly the pattern your HRV 14-day trend is showing. 2. Sleep architecture. Total sleep is steady at ~7h 12m, but Sleep architecture shows a slow rise in REM fragmentation over the same window. 3. Caffeine timing. Your CYP1A2 genotype suggests slow caffeine clearance — the 3pm coffee is still on board at sleep onset. The testable hypothesis is iron deficiency → autonomic suppression. A repeat ferritin in 6–8 weeks (with or without supplementation) would tell us a lot.

Two things worth knowing about — neither one urgent. First, your CAD polygenic score for coronary artery disease sits at the 96th percentile of your ancestry-matched cohort. That doesn't mean disease — it means your polygenic load is elevated. The good news: your LDL-C is currently 94 mg/dL and trending down, your HDL is solid, and your fasting metabolic panel is clean. The genetic load gives you a reason to keep being deliberate about lipids and blood pressure as you age. Second, you carry a CYP2C19 PGx variant at CYP2C19. If a cardiologist ever proposes clopidogrel (Plavix) — for example, after a stent — ask about prasugrel or ticagrelor instead. Same antiplatelet effect, properly activated for your genotype. This is decision-support, not diagnosis. If anything actually changes — a new symptom, new prescription, new lab — bring it back here and we'll re-thread the data.