Table 3.

Univariable linear regression results for muscle strength: between and within models

Variable	Coefficient; 95% CI	P value	Wald test coefficient P value
Income	−0.62; [−0.81, −0.43]	P < 0.001
income_between	−0.73; [−0.97, −0.50]	P < 0.001	−0.41 P = 0.036
income_within	−0.33; [−0.61, −0.04]	P = 0.025
Education	−0.58; [−0.81, −0.36]	P < 0.001
education_between	−0.69; [−0.96, −0.42]	P < 0.001	−0.52 P = 0.020
education_within	−0.17; [−0.53, 0.18]	P = 0.345
Weight	0.06; [0.04, 0.73]	P < 0.001
weight_between	0.05; [0.04, 0.07]	P < 0.001	−0.02 P = 0.242
weight_within	0.07; [0.04, 0.10]	P < 0.001
BMI	0.16; [0.12, 0.21]	P < 0.001
bmi_between	0.16; [0.12, 0.21]	P < 0.001	−0.004 P = 0.928
bmi_within	0.17; [0.09, 0.24]	P < 0.001
Frailty index	10.89; [9.14, 12.64]	P < 0.001
frailty_between	11.97; [10.13, 13.81]	P < 0.001	4.23 P = 0.008
frailty_within	7.74; [4.64, 10.84]	P < 0.001
Gait speed	−8.27; [−9.35, −7.18]	P < 0.001
gaitspeed_between	−8.72; [−9.80, −7.64]	P < 0.001	−1.64 P = 0.050
gaitspeed_within	−7.07; [−8.87, −5.28]	P < 0.001
Physical activity (IPAQ)	−0.55; [−0.84, −0.26]	P < 0.001
ipaq_between	−0.67; [−1.07, −0.28]	P = 0.001	−0.40 P = 0.116
ipaq_within	−0.28; [−0.60, 0.04]	P = 0.090
Healthy eating index	−0.31; [−0.05, −0.01]	P = 0.006
hei_between	−0.04; [−0.07, −0.01]	P = 0.009	−0.03 P = 0.229
hei_within	−0.01; [−0.04, 0.03]	P = 0.679
Protein intake (g/kg)	−1.46; [−2.26, −0.67]	P < 0.001
protein_between	−1.38; [−2.31, −0.44]	P = 0.004	0.36 P = 0.557
protein_within	−1.74; [−2.71, −0.76]	P < 0.001
Appetite (SNAQ)	−0.19; [− 0.33, −0.10]	P = 0.006
snaq_between	−0.72; [−1.55, 0.10]	P = 0.087	−0.59 P = 0.210
snaq_within	−0.13; [−0.31, 0.04]	P = 0.129
Alpha diversity	−0.46; [−0.81, −0.12]	P = 0.011
shannon_between	−0.41; [−0.89, 0.08]	P = 0.104	0.18 P = 0.630
shannon_within	−0.58; [−1.05, −0.11]	P = 0.016

IPAQ, International Physical Activity Questionnaire; SNAQ, Simplified Nutritional Appetite Questionnaire.