Table 4.

Associations Between Airflow Limitation Criteria Alone and Further Refined by FEV₁ and Outcomes

Outcome	No Airflow Limitationa (n = 4,038)	Airflow Limitation
		FR+ and Normal FEV1 (n = 466)	LLN+ and Normal FEV1 (n = 248)	FR+ and Low FEV1b,c (n = 363)	LLN+ and Low FEV1b (n = 304)	FR+ and LLN+ and Low FEV1b (n = 299)
Chronic cough	1.00	1.32 (1.0–1.7)	1.59 (1.12–2.25)	3.32 (2.6–4.3)	3.65 (2.8–4.8)	3.64 (2.78–4.77)
Chronic phlegm	1.00	1.55 (1.1–2.1)	1.83 (1.25–2.67)	3.65 (2.8–4.8)	3.91 (2.9–5.2)	4.10 (3.08–5.46)
Chronic bronchitis	1.00	1.51 (1.0–2.4)	1.60 (0.90–2.82)	3.97 (2.8–5.7)	4.31 (3.0–6.3)	4.48 (3.09–6.51)
Wheeze	1.00	1.59 (1.3–2.0)	2.15 (1.63–2.86)	4.50 (3.5–5.7)	4.60 (3.5–6.0)	4.58 (3.51–5.96)
MRC dyspnea scaled	1.00	1.06 (0.8–1.3)	1.27 (0.95–1.69)	3.65 (2.9–4.6)	3.92 (3.1–5.0)	3.86 (3.03–4.92)
SF-12 Physical scalee	1.00	−0.083 (.85)	–0.85 (.15)	−5.45 (<.01)	−5.56 (<.01)	−5.52 (<.01)
SF-12 Mental scalee	1.00	−0.030 (.95)	−0.22 (.71)	−0.041 (.93)	−0.42 (.44)	−0.42 (.45)
Exacerbation	1.00	1.25 (1.0–1.6)	1.37 (1.01–1.86)	2.39 (1.9–3.0)	2.32 (1.8–3.0)	2.39 (1.84–3.11)
Cardiovascular disease	1.00	1.20 (0.9–1.6)	0.79 (0.52–1.21)	1.51 (1.1–2.0)	1.53 (1.1–2.1)	1.56 (1.15–2.12)

FEV₁ = forced expiratory volume in 1 second; FR = fixed ratio; LLN = lower limit of normal; MRC = Medical Research Council; SF-12 = Short Form 12-item health survey.

Notes: Multiple logistic regression analysis, except as otherwise noted. All models adjusted for age-group (<60 years), sex, and ever smoking. Data are presented as adjusted odds ratios (95% CI) or parameter estimate (P value) from regression analysis.

^aReference group (FR−/LLN−).

^bFEV₁ <80% of predicted.

^cCollectively, these 2 criteria constitute Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 2 or higher disease.

^dOrdinal logistic regression analysis.

^eMultiple linear regression analysis.