The relationship between weight change and inflammatory bowel disease. A population-based cohort study, the HUNT study

Figures & data

Figure 1. The selection of the final study population included participants with follow-up between HUNT1 and HUNT2 (left side) or HUNT2 and HUNT3 (right side), respectively. Participants with a previous inflammatory bowel disease (IBD) diagnosis were excluded.*The participants were excluded because of missing values on BMI in HUNT3. **Data from the two latest HUNT studies was used when there were observations from all three HUNT studies.

Table 1. Characteristics of the study participants.

	Number	% or IQR
Participants	55,896	100%
New IBD cases during follow-up
UC	334	0.6%
CD	54	0.1%
Women	30,194	54.0%
Participation age, in years*
Median, IQR	60.4	48.8 − 71.9
Smoking status*
Never	21,721	38.9%
Previous	18,076	32.3%
Current	13,857	24.8%
Missing	2,242	4.0%
BMI at baseline study
Median, IQR	25.6	23.3 − 28.2
Underweight^1	391	0.7%
Normal weight^2	23,470	42.0%
Overweight^3	23,934	42.8%
Obesity^4	7,937	14.2%
Missing	164	0.3%
BMI at follow-up study
Median, IQR	26.8	24.3 − 29.7
Underweight^1	320	0.6%
Normal weight^2	16,612	29.7%
Overweight^3	25,337	45.3%
Obesity^4	12,882	23.0%
Missing	745	1.3%
Change in BMI
Median, IQR	1.2	−0.1 − 2.6
Between −1 and 1	18,657	33.4%
More than 1	29,080	52.0%
Less than −1	7,301	13.1%
Missing	858	1.5%

*The observations are from the follow-up study. ¹(<18.5 kg/m2), ²(≥18.5 < 25 kg/m2), ³(≥25 < 30 kg/m2), ⁴(≥ 30 kg/m2).

BMI: Body mass index. CD: Crohn’s disease. IBD: Inflammatory bowel disease. UC: Ulcerative colitis. IQR: Interquartile range.

Table 2. The risk of a new UC diagnosis after change in BMI (kg/m²).

Change in BMI	Crude		Adjusted*
	HR	95% CI	HR	95% CI
Change ≤1	1.00	Reference	1.00	Reference
Increase >1	1.16	0.92 − 1.46	1.00	0.78 − 1.26
Decrease >1	0.58	0.38 − 0.90	0.62	0.39 − 0.97

*Adjusted for sex, age and smoking status. BMI: Body mass index. CI: Confidence interval. HR: Hazard ratio. UC: Ulcerative colitis.

Table 3. The risk of a new CD diagnosis after change in BMI (kg/m²).

Change in BMI	Crude		Adjusted*
	HR	95% CI	HR	95% CI
Change ≤1	1.00	Reference	1.00	Reference
Increase >1	1.28	0.68 − 2.44	1.08	0.56 − 2.08
Decrease >1	2.19	1.01 − 4.73	2.01	0.91 − 4.46

*Adjusted for sex, age and smoking status. BMI: Body mass index. CD: Crohn’s disease. CI: Confidence interval. HR: Hazard ratio.

Data availability statement

The data is available through application to HUNT Research Centre: https://hunt-db.medisin.ntnu.no/hunt-db/#/