. 2016 Jun 2;31(10):1156–1163. doi: 10.1007/s11606-016-3750-y

Table 2.

Factors Associated with Changing Trajectories of BMI (kg/m²): Results of Multilevel Modeling

	Entire sample		By sex				By baseline BMI
	(n = 3776)		Female (n = 1849)		Male (n = 1928)		BMI ≥ 24 (n = 1645)		BMI < 24 (n = 2131)
	Raw model	Adjusted model	Raw model	Adjusted model	Raw model	Adjusted model	Raw model	Adjusted model	Raw model	Adjusted model
Fixed effects
Initial status
Intercept	23.073^***	23.483^***	23.045^***	23.720^***	23.075^***	23.027^***	26.302^***	26.182^***	21.085^***	21.597^***
Diabetes	1.294^**	1.228^*	1.894^*	1.693^*	0.780	0.821	−0.025	−0.167	0.403	0.345
Female		−0.154						0.574^*		−0.704^***
Education		0.018		−0.031		0.055^*		−0.014		0.014
Diet control		−0.618^***		−0.955		−0.361^†		−0.106		−0.218
Exercise (≥90 min/week)		−0.039		0.028		−0.091		0.052		−0.136^*
Exercise (1–89 min/week)		−0.042		−0.019		−0.056		0.061		−0.145^*
Alcohol consumption		0.158^**		0.200^†		0.138^*		0.142		0.141^*
Smoking		−0.387^***		−0.598^*		−0.340^***		−0.197		−0.443^***
Hypertension		0.508^***		0.504^***		0.501^**		0.356^***		0.427^***
Heart disease		−0.124^†		−0.086		−0.168^†		−0.182^†		−0.047
Stroke		−0.543^***		−0.696^**		−0.444^**		−0.462^*		−0.502^**
Rate of change
Time	0.080^***	0.086^***	0.078^**	0.062^†	0.084^***	0.104^***	0.039	0.055	0.063^***	0.064^***
Time *diabetes	0.150^*	0.133†	0.119	0.123	0.163^†	0.146	0.209^*	0.212^*	0.104	0.109
Time *female		−0.003						−0.026		0.013
Time diabetesfemale		0.018						0.023		−0.029
Time *education		−0.003^**		−0.001		−0.004^**		−0.001		−0.003^**
Time *diet control		0.002		0.013		−0.005		−0.019		0.005
Time ²	−0.002^**	−0.002^**	−0.002	−0.001	−0.002^**	−0.002^**	−0.002^*	−0.002	0.000	0.000
Time ²*diabetes	−0.008^**	−0.008^*	−0.007	−0.007	−0.008^*	−0.007^*	−0.009^*	−0.010^*	−0.005	−0.005
Random effects
Variance (Intercept)	7.486^***	7.157^***	10.269^***	9.595^***	5.857^***	5.668^***	3.198^***	3.243^***	1.587^***	1.565^***
Variance (slope)	0.056^***	0.046^***	0.096^***	0.092^***	0.037^***	0.022^***	0.087^***	0.083^***	0.001	0
Variance (curvature)	0.0001^***	0.0000^*	0.0001^**	0.0001^**	0.0001^**	0.000	0.0001^**	0.0001^**	0.0000	7.752E-6
Covariance (I & S)	−0.126^*	−0.092	−0.379^**	−0.334^**	−0.026	0.002	−0.234^**	−0.240^*	0.023	0.003
Covariance (I & C)	0.002	0.001	0.010	0.009	−0.001	−0.002	0.007	−0.003^**	−0.002	0.0002^*
Model fit statistics
Deviance (-2LL)	48389.3	45690.4	23287.0	22099.3	24992.9	23471.5	19613.7	18530.3	25460.7	23923.9
Deviance difference test	2698.9(24) ^***		1187.7(20) ^***		1521.4(20) ^***		1083.4(24) ^***		1536.8(24) ^***

(1) ^*** p < 0.001, ^** p < 0.01, ^* p < 0.05, ^† p < 0.08; (2) the participants’ time of the BMI scores were coded to reflect the number of years before diabetes diagnosis (−18 ∼ 0). In this table, we centered time to −18. The intercept (time = 0) thus represents 18 years before diabetes diagnosis. (3) Based on results of the raw model, for adults who developed diabetes, their linear rate of change in BMI is 0.23 kg/m² and curvature is −0.01 kg/m². Before the turning point (-(β_time + β_{diabetes*time})/2(β_time ² + β_{diabetes*time} ² = 11.5), they accumulate a total of 1.3225 kg/m²(0.23*11.5 + (−0.01)*11.5²) during 11.5 years. In this sense, they have an annual rate of BMI change of 0.115 kg/m²(1.3225 kg/m²/11.5 years = 0.115 kg/m² per year)