Symptoms and lung function decline in a middle-aged cohort of males and females in Australia

Figures & data

Table 1 The number (%) of participants with respiratory symptoms or allergies by sex and survey

Respiratory symptom or allergy	Males (n=147)		Females (n=171)		P-value comparing surveysa	P-value comparing sexb	P-value for sex × time interactionc
	1993	2013	1993	2013
Wheeze	53 (36%)	39 (27%)	75 (44%)	46 (27%)	<0.001	0.385	0.250
SOB after activity	45 (31%)	59 (40%)	64 (37%)	73 (43%)	0.018	0.262	0.504
Nocturnal cough	39 (27%)	38 (26%)	70 (41%)	58 (34%)	0.289	0.006	0.405
Morning sputum	24 (16%)	17 (12%)	11 (6%)	11 (7%)	0.405	0.008	0.385
Nasal allergies	64 (44%)	74 (50%)	91 (53%)	95 (56%)	0.061	0.132	0.408
Skin allergies	66 (45%)	53 (36%)	92 (54%)	78 (46%)	0.004	0.049	0.814
Current asthma	32 (22%)	36 (24%)	42 (25%)	48 (28%)	0.105	0.474	0.881

Notes:

a P-value calculated from logistic regression (with GEEs) – marginal effect of time,

b P-value calculated from logistic regression (with GEEs) – marginal effect of sex, and

c P-value calculated from logistic regression (with GEEs) interaction for sex × time.

Abbreviations: GEE, generalized estimating equations; SOB, shortness of breath.

Table 2 Baseline and follow-up characteristics of subjects who had spirometry in 1993 and 2013

	Males Mean (SD) (n=130)	Females Mean (SD) (n=132)
Baseline characteristics (1993)
Age (years)	35.6 (5.9)	35.1 (6.4)
Weight (kg)	80.3 (11.9)	64.8 (11.9)*
BMI (kg/m^2)	25.8 (2.8)	24.5 (4.1)†
FEV1 (L)	4.02 (0.7)	3.0 (0.4)*
(% predicted)	94.7 (14.0)	97.0 (11.5)
FVC (L)	5.25 (0.77)	3.82 (0.66)*
(% predicted)	99.5 (11.5)	102.4 (13.1)
FEV1/FVC (%)	77 (7.2)	79 (6.8)‡
Smoking status (%)
Never smoked	52.3	56.1
Former smoker	26.9	24.2
Current smoker	20.8	19.7
Characteristics on follow-up (2013)
Age (years)	55.4 (5.9)	55.0 (6.3)
Age difference (years)	19.8 (0.59)	19.8 (0.58)
Weight (kg)	87.4 (16.5)	72.9 (16.3)*
Weight difference (kg)	7.0 (9.1)	8.1 (9.8)
BMI (kg/m^2)	27.9 (4.4)	27.7 (5.9)
ΔBMI 1993–2013 (kg/m^2)	2.2 (2.97)	3.2 (3.8)**
FEV1(L)	3.61 (0.68)	2.52 (0.46)*
FVC (L)	4.84 (0.8)	3.35 (0.6)*
ΔFEV1 in mL/year	21.4 (19.4)	24.7 (14.4)
ΔFVC in mL/year	21.1 (20.1)	24.7 (20.2)
FEV1/FVC decline (%)	2.2 (5.0)	3.4 (5.4)
Current smoker (%)	6.9	7.7
Pack-years for current smokers 2013 median (IQR)	13.6 (11.0, 35.3)	28.4 (7.8, 33.8)

Notes:

* P<0.001,

** P=0.014,

† P=0.004,

‡ P=0.006.

Abbreviations: ΔBMI, change in body mass index; ΔFEV₁, rate of decline over time in forced expiratory volume in 1 second (mL/year); ΔFVC, rate of decline over time in forced vital capacity (mL/year); IQR, interquartile range; SD, standard deviation.

Table 3 Multiple regression coefficients (with 95% CI) for associations between decline in FEV₁ and clinical characteristics

Predictors	Males (n=130)	Females (n=132)
Age (1993)	1.2 (0.6, 1.7)	0.85 (0.5, 1.2)
Baseline FEV1	13.3 (8.3, 18.3)	10.8 (5.7, 15.9)
Maternal smoking	9.4 (2.8, 16)	NS
Pack-years smoked by 2013	NS	0.37 (0.07, 0.67)
Height (1993)	−0.8 (−1.2, −0.3)	NS
ΔBMI	NS	1.3 (0.7, 1.8)

Note: Other covariates were not included in the final model.

Abbreviations: ΔBMI, change in body mass index; CI, confidence interval; NS, not significant, that is, covariate were not entered in final regression model.

Figure 1 Mean (with 95% CI) decline in FEV₁ mL/year by smoking at baseline.

Abbreviation: CI, confidence interval.

Table 4 Multiple regression coefficients (with 95% CI) for associations between decline in FVC and clinical characteristics

Predictors	Males (n=130)	Females (n=132)
Age (1993)	1.1 (0.6, 1.7)	1.4 (1.0, 1.8)
Baseline FVC	10.4 (5.2, 15.7)	20.4 (15.0, 25.8)
Height (1993)	−0.7 (−0.1, −1.3)	−0.6 (−0.1, −1.1)
ΔBMI	2.0 (0.9, 3.1)	1.8 (1.0, 2.5)

Note: Other covariates were not included in the final model.

Abbreviations: ΔBMI, change in body mass index; CI, confidence interval.

Figure 2 Mean decline in FVC (mL/year) over time categorized by baseline BMI (kg/m²) in males and females.

Abbreviation: BMI, body mass index.