TABLE 2

Absolute forced expiratory volume in 1 s (FEV1) and sex-related difference in breathlessness

ModelWithout absolute FEV1With absolute FEV1Percentage of sex variance in breathlessness explained by absolute FEV1
Females versus males OR (95% CI)Variance explained by sexFemales versus males OR (95% CI)Variance explained by sex
Crude2.21 (1.79–2.72)4.80.89 (0.69–1.14)0100
Risk factors2.52 (2.01–3.11)5.21.18 (0.88–1.59)0.198
Diseases2.28 (1.90–2.77)4.70.99 (0.78–1.26)0100
Physiology2.56 (2.07–3.16)5.21.13 (0.79–1.61)0100
Final2.63 (2.12–3.25)5.11.29 (0.89–1.88)0.198
  • Sex difference in breathlessness expressed as odds ratios (OR) of more severe breathlessness for females compared with males in models with or without the absolute value of FEV1 (n=3250). The sex estimates were crude and adjusted for risk factors (pack-years of smoking, exercise, occupational exposure, lung infection at age <5 years and hypertension); diseases (asthma, chronic bronchitis, chronic airflow limitation (CAL), ischaemic heart disease (IHD) and history of cancer or depression); and physiology (age, body mass index (BMI) and CAL). The final model was controlled for age, BMI, chronic bronchitis, CAL, pack-years smoking, exercise, IHD and history of depression. Analysis performed using ordinal logistic regression clustering on country with 3250 participants in all models. The variance in modified Medical Research Council scores explained by sex was measured as the difference in variance explained by the model with sex compared to the model without sex, using McKelvey and Zavoina's R2 [23].