Table 2.

Hazard ratios (95% CIs) of incident asthma with weight change patterns across adulthood in NHANES 1999–2016

Weight change patterns	No. of incident asthma/person-years	Model 1a		Model 2b
		HR (95% CI)	P	HR (95% CI)	P
Category 1c
Stable non-obesity	402/151,360	1		1
Non-obesity to obesity	165/39,485	1.66 (1.30, 2.11)	< 0.001	1.63 (1.29, 2.07)	< 0.001
Obesity to non-obesity	7/2067	1.47 (0.50, 4.27)	0.479	1.21 (0.41, 3.62)	0.730
Stable obesity	53/12,305	1.48 (1.02, 2.16)	0.041	1.41 (0.97, 2.05)	0.075
Category 2d
Weight loss ≥ 2.5 kg	33/11,163	1.01 (0.60, 1.72)	0.964	0.91 (0.53, 1.56)	0.725
Weight change within 2.5 kg	126/48,635	1		1
Weight gain ≥ 2.5 kg and < 10 kg	180/66,293	0.95 (0.70, 1.30)	0.744	0.99 (0.73, 1.34)	0.938
Weight gain ≥ 10 kg and < 20 kg	139/46,712	1.15 (0.85, 1.56)	0.372	1.19 (0.88, 1.60)	0.253
Weight gain ≥ 20 kg	149/32,414	1.52 (1.14, 2.03)	0.005	1.53 (1.15, 2.03)	0.004

All estimates accounted for complex survey designs

^aModel 1 was adjusted for baseline age, gender, race/ethnicity

^bModel 2 was additionally adjusted for education level, family income-poverty ratio level, smoking status, and family history of asthma. In the Category 2 analyses, we also included BMI at the age 25 years as potential confounders in model 2

^cStable non-obesity, BMI_{age 25} < 30 kg/m² and BMI_{10 years prior} < 30; non-obesity to obesity, BMI_{age 25} < 30 kg/m² and BMI_{10 years prior} ≥ 30; obesity to non-obesity, BMI_{age 25} ≥ 30 kg/m² and BMI_{10 years prior} < 30; stable obesity, BMI_{age 25} ≥ 30 kg/m² and BMI_{10 years prior} ≥ 30

^dAbsolute weight change: weight loss of at least 2.5 kg, weight change within 2.5 kg, weight gain of at least 2.5 kg but less than 10.0 kg, weight gain of at least 10.0 kg but less than 20.0 kg, and weight gain of at least 20.0 kg