Table 5.

Sensitivity analyses. Multivariable linear regression models with the outcome of femoral neck bone mineral density (g/cm²).

Variables	β	95% CI	p-Value
Sensitivity analysis 1: entire cohort, substituting appendicular lean mass index (ALMI) and fat mass index (FMI) for body mass index (BMI). N = 135, R2 = 0.36.
Age	−0.003	−0.005 to −0.001	0.002
Female sex	−0.028	−0.095 to 0.040	0.419
High positive anti-CCPa	−0.048	−0.089 to −0.008	0.019
Disease duration (years)	−0.001	−0.003 to 0.001	0.556
Appendicular LMIb	0.040	0.016 to 0.063	0.001
FMIb	0.002	−0.004 to 0.007	0.602
Frailtyc
Robust	Ref	–	–
Pre-frail	−0.056	0.111 to −0.002	0.043
Frail	−0.051	−0.139 to 0.037	0.252
Sensitivity analysis 2: entire cohort, restricted to subjects who did not report osteoporosis medication use. N = 86, R2 = 0.29.
Age	−0.002	−0.005 to 0.001	0.095
Female sex	−0.097	−0.179 to −0.015	0.021
High positive anti-CCPa	−0.044	−0.097 to 0.009	0.106
Disease duration (years)	−0.002	−0.004 to 0.001	0.239
BMIb	0.006	0.002 to 0.011	0.007
Frailtyc
Robust	Ref	–	–
Pre-frail	−0.044	−0.111 to 0.023	0.194
Frail	−0.111	−0.250 to 0.028	0.115
Sensitivity analysis 3: entire cohort, substituting individual Fried frailty subcomponents for the composite frailty variable. N = 128, R2 = 0.28.
Age	−0.003	−0.006 to −0.001	0.002
Female sex	−0.071	−0.131 to −0.011	0.021
High positive anti-CCPa	−0.058	−0.103 to −0.013	0.011
Disease duration (years)	−0.001	−0.003 to 0.001	0.261
BMIb	0.007	0.003 to 0.011	0.001
Frailty componentsd
Low weight	0.113	−0.032 to 0.257	0.125
Exhaustion	−0.042	−0.098 to 0.014	0.144
Low gait speed	0.044	−0.045 to 0.133	0.133
Low grip strength	−0.056	−0.102 to −0.010	0.017
Low physical activity	−0.027	−0.076 to 0.022	0.283

All variables included in the multivariate models are shown in table.

CCP: cyclic citrullinated peptide antibody; BMI: body mass index; DXA: dual x-ray absorptiometry; LMI: lean mass index; FMI: fat mass index.

^aHigh positive anti-CCP defined as level three times the upper limit of normal (>60 units) based on the 2010 EULAR/ACR RA classification criteria (Aletaha et al., 2010). This threshold was used to minimize heterogeneity of this group.

^bAppendicular LMI, FMI, and BMI (kg/m²).

^cCategories based on Fried Frailty Index (Fried et al., 2001) (score of 0 = robust; 1–2 = pre-frail; 3+ = frail).

^dLow weight was based on BMI. Exhaustion was based on patient self-report. Low gait speed is based on the 4-meter walking speed test. Low grip strength is measured by hand-held dynamometer. Low physical activity was based on the International Physical Activity Questionnaire (Giles et al., 2008a).