Table 2 Latent linear spline SEM to test modification of GRS associations with BMI trajectories by physical activity

From: Modification of genetic influences on adiposity between 36 and 63 years of age by physical activity and smoking in the 1946 British Birth Cohort Study

  

BMI (kg m−2), N=2216

 

Parameter a

B (95% CI), P-value

Intercept

 

Size 36 years

 GRS (per risk allele)b

A

0.312 (0.196, 0.428), <0.001

 PA at age of interceptc

Inactive (referent)

 

−−

Active

B

−0.813 (−1.113, −0.512), <0.001

 GRS-by-PA at age of intercept

Inactive (referent)

 

−−

Active

C

−0.189 (−0.331, −0.047), 0.009

Slope 1

 

Change per year 36–53 years

 GRS (per risk allele)b

D

0.001 (−0.005, 0.007), 0.7

 PA at age of interceptc

Inactive (referent)

 

−−

Active

E

0.004 (−0.011, 0.019), 0.6

 GRS-by-PA at age of intercept

Inactive (referent)

 

−−

Active

F

0.000 (−0.008, 0.007), 0.9

Slope 2

 

Change per year 53–63 years

 GRS (per risk allele)b

G

0.005 (−0.004, 0.014), 0.3

 PA at age of knotc

Inactive (referent)

 

−−

Active

H

−0.018 (−0.043, 0.008), 0.2

 GRS-by-PA at age of knot

Inactive (referent)

 

−−

Active

I

−0.012 (−0.024, −0.001), 0.04

  1. Abbreviations: BMI, body mass index; GRS, genetic risk score; PA, physical activity; SEM, structural equation model.
  2. aEach parameter is labelled with a letter that corresponds to a thick arrow in the visual representation of this SEM in Figure 1.
  3. bComputed for each individual as the summation of risk alleles across 11 obesity variants.
  4. Participation in leisure time PA was ascertained at each age during an interview with a research nurse. Leisure time PA assessment was based on the Minnesota leisure-time physical activity questionnaire at 36 years of age and on more basic questions at 53 years of age. At each age, participants who reported no leisure time PA were classified as ‘inactive’ and those who reported any relevant activity (in the previous month at 36 years of age and in the previous 4 weeks at 53 years of age) were classified as ‘active’.
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