Table 1.

Population characteristics and respiratory symptom prevalence.

Characteristic	Lifelines	UK Biobank	UK Biobank
	$n=\mathrm{52,064}$	Wheeze and ${\text{NO}}_2$ analyses; $n=\mathrm{350,639}$	Shortness of breath and ${\text{NO}}_2$ analyses; $n=\mathrm{121,550}$
Male, % ($n$)	43.2 (22,487)	47.3 (165,717)	47.3 (57,486)
Female, % ($n$)	56.8 (29,577)	52.7 (184,922)	52.7 (64,064)
Age, $\text{mean}\pm \text{SD}$	$42.6\pm 11.5$	$56.2\pm 8.1$	$56.5\pm 8.1$
Age, % ($n$)
$<65\mathrm{y}$	96.5 (50,233)	82.5 (289,278)	81.2 (98,689)
$\ge 65\mathrm{y}$	3.5 (1,831)	17.5 (61,361)	18.8 (22,861)
BMI, % ($n$)
Normal ($<25{\mathrm{kg}/\mathrm{m}}^2$)	47.4 (24,650)	33.3 (116,585)	33.5 (40,767)
Overweight ($25–29.9{\mathrm{kg}/\mathrm{m}}^2$)	38.7 (20,146)	43 (150,657)	42.6 (51,735)
Obese ( $\ge 30{\mathrm{kg}/\mathrm{m}}^2$)	14 (7,268)	23.8 (83,397)	23.9 (29,048)
Education level, % ($n$)
Secondary education or lower, % ($n$)	24.9 (12,936)	35.3 (123,925)	34.3 (41,676)
Postsecondary education, % ($n$)	75.1 (39,128)	64.7 (226,714)	65.7 (79,874)
Household income, % ($n$)
Mean or below mean country-specific net disposable income	48.4 (25,215)	45.2 (158,600)	45.2 (54,903)
Higher than mean country-specific net disposable income	51.6 (26,849)	54.8 (192,039)	54.8 (66,647)
Smoking status, % ($n$)
Current smoker	23.7 (12,345)	3 (10,453)	3 (3,670)
Former smoker	30.4 (15,813)	38.1 (133,703)	38 (46,191)
Never smoker	45.9 (23,960)	58.9 (206,483)	59 (71,689)
Passive smoking exposure, % ($n$)
Not exposed to secondhand smoke at home or at work	73.5 (38,264)	77.74 (272,604)	77.9 (94,708)
Exposed to secondhand smoke at home or at work	26.5 (13,800)	22.26 (78,035)	22.1 (26,842)
Wheeze, % ($n$)
Has not had wheeze symptoms	79.7 (41,466)	81.6 (286,276)	—
Has had wheeze symptoms	20.4 (10,596)	18.4 (64,363)	—
Shortness of breath, %a ($n$)
Has not had shortness of breath symptoms	90 (46,859)	—	90.2 (109,584)
Has had shortness of breath symptoms	10 (5,205)	—	9.8 (11,966)
Asthma, %b ($n$)
Has had asthma	8.1 (4,203)	11.6 (40,680)	11.5 (13,967)
Has not had asthma	91.9 (47,686)	88.4 (309,729)	88.5 (107,495)

Note: For participants with complete data in fully adjusted model for age, sex, BMI, income, education, smoking status, passive smoking exposure. —, UK Biobank wheeze prevalence shown in second data column and shortness of breath prevalence shown in third data column; BMI, body mass index; SD, standard deviation.

^aOnly 35% of UK Biobank subjects had data for shortness of breath because it was added to the baseline survey late in the recruitment phase (i.e., as of 2009).

^bAn additional 175 participants had missing data for the asthma status variable in Lifelines. In the UK Biobank, 230 participants and 88 participants had missing data for asthma status for wheeze and ${\text{NO}}_2$ analyses and shortness of breath and ${\text{NO}}_2$ analyses, respectively.