Serum brain-derived neurotrophic factor: Determinants and relationship with depressive symptoms in a community population of middle-aged and elderly people

Figures & data

Table I. Population characteristics.

Authors	N = 1230
BDNF (ng/ml, SD)	7.79 (3.32)
BDI sum score (median, IQR)	4 (2–7)
% with history of depression (n)	16.9 (208)
Sampling
% sampling in the morning (n)	79.2 (974)
Months in storage (SD)	23.7 (9.5)
Sociodemographics
% female (n)	49.9 (614)
Age (mean in years, SD)	61.2 (5.9)
% living alone (n)	21.4 (263)
Health indicators
% current smoker (n)	16.1 (195)
% severe alcohol use (n)	11.8 (145)
% 2 or more hours of physical activity p/w (n)	36.6 (450)
Disease
% metabolic syndrome (n)	27.8 (342)
% coronary artery disease (n)	6.7 (83)
% somatic co-morbidity other than CAD (n)	11.0 (135)

BDNF, brain-derived neurotrophic factor; SD, standard deviation; BDI, Beck Depression inventory; IQR, interquartile range; CAD, coronary artery disease.

Figure 1. Interactice effect of age and gender on serum BDNF level.*

Table II. Results of the univariate and multivariate analyses per category.

	Univariate		Multivariate
	r	P	B	95% CI of B	SE	β	t	P
Model 1 (Sampling variables)
Time of day (0=AM, 1=PM)	−0.069	0.008	−0.573	−1.03 – −0.12	0.233	−0.070	−2.459	0.014
Time in storage (days)	−0.014	0.31	0.000	0.00 – 0.00	0.000	−0.017	−0.610	0.54
Model 2 (Demographic variables)
Age (years deviating from mean age)	−0.112	<0.001	0.0012	−0.03 – 0.06	0.022	0.022	0.561	0.58
Sex (0=male, 1=female)	0.035	0.11	0.181	−0.19 – 0.55	0.190	0.027	0.956	0.34
Interaction age × sex	n/a	n/a	−0.151	−0.21 – −0.09	0.032	−0.187	−4.734	<0.001
Marital status (1=living alone, 2=living together)	−0.041	0.08	−0.276	−0.73 – 0.18	0.231	−0.034	−1.199	0.23
Model 3 (Health variables)
Alcohol use (male>21/week; female > 14/week)	−0.028	0.16	−0.401	−0.98 – 0.17	0.294	−0.039	−1.362	0.17
Current smoker (0=no, 1=yes)	0.094	<.001	0.872	0.37 – 1.38	0.258	0.097	3.379	0.001
Physical activity (0=≤ 1 hrs/week, 1=≥2 hrs/week)	−0.023	0.22	−0.082	−0.47 – 0.30	0.197	−0.012	−0.416	0.68
Model 4 (Disease variables)
Metabolic Syndrome (IDF) (0=no, 1=yes)	0.007	0.39	0.035	−0.32 – 0.39	0.182	0.005	0.191	0.85
Coronary artery disease (0=no, 1=yes)	0.011	0.35	−0.043	−0.71 – 0.63	0.341	−0.003	−0.126	0.90
Somatic co-morbidty other than CAD (0=no, 1=yes)	0.044	0.05	0.473	−0.08 – 1.02	0.280	0.044	1.690	0.09

R, Pearson's correlation coefficient; B, regression coefficient; CI, confidence interval; SE, standard error of the mean; β, standardized correlation coefficient; CAD, coronary artery disease.

Table III. Final model with BDI scores corrected for potential confounders.

	B	95% CI of B	SE	β	t	p
Constant	7.959	7.6 – 8.4	0.208		38.277	.000
BDI (log-transformed)	0.607	−1.13 – −0.09	0.265	−0.060	−2.296	.022
Age (yrs)	0.006	−0.05 – 0.03	0.020	0.011	−0.304	.761
Sex (0=male; 1=female)	0.293	−0.04 – 0.63	0.170	.045	1.724	.085
Interaction age × sex	0.110	−0.17 – −0.05	0.028	−0.138	−3.873	.000
Time of day (0=AM; 1=PM)	0.405	−0.80 – −0.01	0.204	−0.050	−1.985	.047
Current smoker (0=no; 1=yes)	0.613	0.19 – 1.06	0.215	0.072	2.843	.005
Somatic co-morbidity (0=no; 1=yes)	0.515	−0.03 – 1.06	0.278	0.047	1.857	.063

B, regression coefficient; CI, confidence interval; SE, standard error of the mean; β, standardized correlation coefficient.