Female-to-Male Ratio in Primary PAH
The female-to-male ratio for idiopathic (primary) pulmonary arterial hypertension is 1.7:1 1, 2.
Epidemiologic Data
The most authoritative data comes from the ACCF/AHA 2009 Expert Consensus Document, which clearly states that idiopathic PAH (IPAH) has a female/male ratio of 1.7:1 with a mean age at diagnosis of 37 years 1. This ratio was confirmed by the National Institutes of Health registry data from 187 patients, which documented the same 1.7:1 female predominance 2.
Important Context and Variations
While the overall ratio for IPAH is 1.7:1, the female predominance varies significantly depending on the specific PAH subtype and associated conditions:
Broader PAH Categories:
- General pulmonary hypertension (all types): 1.8:1 female-to-male ratio 3
- Pulmonary arterial hypertension subtype specifically: Up to 4:1 female predominance 4, 5, 6
- Adult PAH (broader definition): 2:1 to 4:1 female-to-male ratio 7
Associated PAH Conditions:
- Connective tissue disease-associated PAH: Dramatically skewed at 9:1 female-to-male ratio 8
- Hereditary PAH with BMPR2 mutations: Shows incomplete penetrance with female predominance only after puberty, suggesting hormonal influence 7
Clinical Significance
The female predominance is paradoxical because despite higher incidence in women, they demonstrate:
- Better baseline right ventricular function 9, 10
- Superior hemodynamic indices (higher PA pulsatility index and RV stroke work index) 9
- Better response to endothelin receptor antagonists and prostacyclins 10
- Lower mortality risk compared to men (adjusted HR 0.60) 11
This "estrogen paradox" suggests that while female sex hormones may increase susceptibility to developing PAH, they may simultaneously provide protective effects on RV adaptation and overall survival 12.
Key Caveat
The age of PAH patients has been increasing over time. While the original NIH registry from 1981 showed a mean age of 36 years, current registries show mean ages between 50-65 years, and the female predominance may not be present in elderly patients 3. This temporal shift emphasizes that the 1.7:1 ratio represents the classic presentation but may not fully capture contemporary epidemiology in older populations.