The impact of body mass index, central obesity and physical activity on lung function: results of the EpiHealth study

Magnus Svartengren; Gui-Hong Cai; Andrei Malinovschi; Jenny Theorell-Haglöw; Christer Janson; Sölve Elmståhl; Lars Lind; Erik Lampa; Eva Lindberg

doi:10.1183/23120541.00214-2020

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FIGURE 1
a) Forced expiratory volume in 1 s (FEV₁) z-scores and 95% confidence intervals (CIs) in men and women as a function of waist circumference (WC) predicated on body mass index (BMI) values of 20, 25 and 30 kg·m^–2 (chosen to correspond to the widely used cut-offs for the normal weight, overweight and obese categories). b) FEV₁ z-scores and 95% CIs in men and women as a function of BMI predicated on WC (in cm) corresponding roughly to the gender specific 10th, 50th and 90th percentiles rounded to the nearest multiple of five. All estimates were adjusted for smoking status and education.
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FIGURE 2
a) Estimated forced vital capacity (FVC) z-scores and 95% confidence intervals (CIs) in men and women as a function of waist circumference (WC) predicated on body mass index (BMI) values of 20, 25 and 30 kg·m^–2 (chosen to correspond to the widely used cut-offs for the normal weight, overweight and obese categories). b) Estimated FVC z-scores and 95% CIs in men and women as a function of BMI predicated on WC (in cm) corresponding roughly to the gender specific 10th, 50th and 90th percentiles rounded to the nearest multiple of five. All estimates were adjusted for smoking status and education.
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FIGURE 3
a) Mean forced vital capacity (FVC) z-scores and 95% confidence intervals (CIs) for different categories of physical activity. b) Mean forced expiratory volume in 1 s (FEV₁) z-scores and 95% CIs for different categories of physical activity. Mean values and 95% CIs were adjusted for body mass index (BMI), waist circumference (WC), gender, smoking status and education. Age was not included in the models since it was already adjusted for in the predicted values used as outcome variables.

Tables

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TABLE 1

Characteristics of the study participants in total and stratified by obesity level and central obesity

Characteristic	Category	Total (n=22 743)	Obesity
			Mild^# (n=3454)	Morbid^¶ (n=128)	Central⁺ (n=9327)
Gender	Men	43.8	47.8	27.3	34.5
	Women	56.2	52.2	72.7	65.5
Age^§ years	<55	28.1	27.2	34.3	22.9
	55–64	31.8	32.6	32.8	32.3
	≥65	40.1	40.4	32.8	44.8
Smoking status	Never	44.7	40.2	35.8	38.9
	Former	47.4	51.9	56.9	52.3
	Current	8.0	7.9	7.3	8.8
Leisure time physical activity	Low	6.0	12.3	21.1	9.0
	Medium	75.9	78.0	76.4	80.9
	High	18.1	9.6	2.4	10.1
Education	Primary and elementary school	27.4	34.0	28.0	32.5
	Secondary high school	25.6	30.1	28.8	26.8
	University	47.0	35.9	43.2	40.8

Data are presented as %. ^#: body mass index (BMI) 30–39 kg·m⁻²; ^¶: BMI ≥40 kg·m⁻²; ⁺: waist circumference (WC) ≥88 cm for women and ≥102 cm for men; ^§: mean age: 60 years.

TABLE 2

Lung function variables stratified by obesity, central obesity and level of leisure time physical activity

Variable	Total (n=22 743)	Obesity			Central obesity		Leisure time physical activity
Variable	Total (n=22 743)	No^# (n=18 550)	Mild^¶ (n=3454)	Morbid⁺ (n=128)	No (n=13 412)	Yes^§ (n=9327)	High (n=4012)	Medium (n=16 805)	Low (n=1326)
FEV₁ % predicted	100 (91–111)	101 (98–112)	98 (88–109)	88 (80–100)	102 (93–112)	99 (88–109)	103 (94–113)	101 (91–111)	97 (86–107)
FVC % predicted	100 (91–111)	101 (92–111)	95 (86–106)	85 (78–96)	102 (93–112)	97 (87–107)	103 (94–113)	100 (90–110)	96 (85–106)
FEV₁/FVC % predicted	100 (96–110)	100 (95–110)	103 (98–108)	104 (75–85)	100 (95–110)	100 (97–110)	101 (95–105)	101 (96–106)	102 (95–107)
FEV₁ z-score	0.06 (−0.62 to 0.77)	0.10 (−0.56 to 0.80)	−0.12 (−0.84 to 0.60)	−0.82 (−1.37 to −0.01)	0.14 (−0.50 to 0.86)	−0.08 (−0.79 to 0.61)	0.19 (−0.42 to 0.91)	0.04 (−0.64 to 0.75)	−0.22 (−0.94 to 0.52)
FVC z-score	0.00 (−0.64 to 0.70)	0.07 (−0.56 to 0.76)	−0.31 (−0.97 to 0.39)	−1.05 (−1.58 to −0.22)	0.14 (−0.48 to 0.84)	−0.21 (−0.86 to 0.48)	0.20 (−0.43 to 0.88)	−0.02 (−0.65 to 0.67)	−0.31 (−1.03 to 0.45)
FEV₁/FVC z-score	0.06 (−0.57 to 0.64)	0.02 (−0.62 to 0.58)	0.30 (−0.31 to 0.86)	0.45 (−0.28 to 0.90)	−0.01 (−0.65 to 0.56)	0.18 (−0.45 to 0.74)	0.03 (−0.64 to 0.58)	0.07 (−0.55 to 0.63)	0.14 (−0.62 to 0.77)

Data are presented as median (IQR). FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; IQR: interquartile range. ^#: body mass index (BMI) <30 kg·m⁻²; ^¶: BMI 30–39 kg·m⁻²; ⁺: BMI ≥40 kg·m⁻²; ^§: waist circumference (WC) ≥88 cm for women and ≥102 cm for men.

TABLE 3

Lung function variables stratified by body mass index (BMI) category in participants with and without central obesity

Variable	Participants without central obesity ^# (n=13 412)				Participants with central obesity^# (n=9327)
Variable	Underweight^¶ (n=541)	Normal weight⁺ (n=7515)	Overweight^§ (n=4924)	Mild obesity^f (n=177)	Normal weight⁺ (n=914)	Overweight^§ (n=4654)	Mild obesity^f (n=3277)	Morbid obesity ^## (n=128)
FEV₁ % predicted	99 (90–109)	102 (93–112)	103 (93–113)	105 (96–115)	99 (89–109)	100 (90–110)	98 (88–109)	88 (80–100)
FVC % predicted	100 (91–111)	102 (94–113)	102 (92–112)	103 (94–113)	98 (89–109)	98 (89–109)	95 (86–106)	85 (78–96)
FEV₁/FVC % predicted	98 (92–103)	100 (94–105)	101 (96–106)	104 (100–108)	100 (94–105)	102 (96–106)	103 (98–108)	104 (98–108)
FEV₁ z-score	−0.06 (−0.73 to 0.60)	0.12 (−0.51 to 0.82)	0.19 (−0.47 to 0.92)	0.38 (−0.26 to 1.10)	−0.06 (−0.73 to 0.59)	0.00 (−0.69 to 0.67)	−0.12 (−0.84 to 0.60)	−0.82 (−1.37 to −0.01)
FVC z-score	0.00 (−0.61 to 0.74)	0.15 (−0.44 to 0.85)	0.13 (−0.51 to 0.83)	0.17 (−0.47 to 0.92)	−1.10 (−0.72 to 0.61)	−0.12 (−0.74 to 0.57)	−0.31 (−0.97 to 0.39)	−1.05 (−1.58 to −0.22)
FEV₁/FVC z-score	−0.27 (−1.00 to 0.30)	−0.08 (−0.69 to 0.47)	0.12 (−0.53 to 0.68)	0.39 (−0.08 to 0.90)	−0.07 (−0.74 to 0.48)	0.13 (−0.48 to 0.69)	0.30 (−0.31 to 0.86)	0.44 (−0.28 to 0.90)

Data are presented as median (IQR). The combination of underweight and central obesity is not presented since only two subjects were in this category. FEV₁: forced expiratory volume in 1 s; FVC: forced vital capacity; IQR: interquartile range. ^#: waist circumference (WC) ≥88 cm for women and ≥102 cm for men; ^¶: BMI <20 kg·m⁻²; ⁺: BMI 20–24 kg·m⁻²; ^§: BMI 25–29 kg·m⁻²; ^f: BMI 30–39 kg·m⁻²; ^##: BMI ≥40 kg·m⁻².

TABLE 4

Estimated differences in forced expiratory volume in 1 s (FEV₁) with 95% confidence intervals (CIs) stratified by both changes in body mass index (BMI) and waist circumference (WC) at a fixed level of the other variable

	Comparison between WC values cm	BMI kg·m⁻² (fixed level)	FEV₁ z-score (estimated difference)	95% CI
Men	90 versus 70	20	−0.44	−0.78 to −0.10
	105 versus 85	25	−0.56	−0.70 to −0.42
	115 versus 95	30	−0.83	−0.96 to −0.69
Women	85 versus 65	20	−0.21	−0.35 to −0.06
	95 versus 75	25	−0.36	−0.45 to −0.28
	105 versus 85	30	−0.34	−0.48 to −0.20
	Comparison between BMI values kg·m⁻²	WC cm (fixed level)	FEV₁ z-score (estimated difference)	95% CI
Men	28 versus 22	90	0.48	0.33–0.63
	30 versus 24	100	0.39	0.26–0.52
	32 versus 26	105	0.31	0.20–0.42
Women	26 versus 20	80	0.32	0.23–0.42
	28 versus 22	90	0.27	0.18–0.36
	30 versus 24	95	0.21	0.11–0.31