Table 3. Serum BDNF levels and characteristics at baseline survey by the groups of mood disorders developed between 2008 and 2012 and the control group.
| Controls (n=106) | Major depressive disorder (n=28) | Minor depressive disordera (n=39) | Minor depressive episodeb with history of major depressive episode (n=8) | P-value | |
|---|---|---|---|---|---|
| Serum BDNF, ng ml−1 | 12.6 (3.6) | 13.9 (3.1)c | 13.6 (2.6) | 14.5 (3.2) | 0.090 |
| Age at baseline, years | 77.9 (2.3) | 77.0 (2.2) | 78.3 (2.4) | 77.6 (3.2) | 0.209 |
| Educational level at middle school or less, % | 22.6 | 25.0 | 25.6 | 37.5 | 0.811 |
| Living alone, % | 34.0 | 21.4 | 33.3 | 33.3 | 0.644 |
| Smoker, % | 6.6 | 3.6 | 2.6 | 0.0 | 0.643 |
| Drinking alcohol 5 days or more per week, % | 8.5 | 17.9 | 5.1 | 12.5 | 0.336 |
| Sports or exercise activity with 1 day or less per week, % | 66.0 | 71.4 | 82.1 | 62.5 | 0.291 |
| Body mass index, kg/m2 | 22.8 (3.6) | 22.2 (2.6) | 22.1 (2.8) | 22.3 (3.0) | 0.559 |
| History of heart diseases, % | 16.0 | 21.4 | 28.2 | 28.6 | 0.386 |
| Prescribed steroid, % | — | — | 2.6 | — | 0.300 |
| Blood drawing in the afternoon, % | 31.1 | 32.1 | 48.7 | 62.5 | 0.094 |
| Fasting at blood drawing, % | 0.9 | — | — | — | 0.868 |
| Storage duration of sera, months | 64.4 (0.5) | 65.0 (0.6) | 64.7 (0.5) | 64.8 (0.7) | 0.000 |
Abbreviation: BDNF, brain-derived neurotrophic factor.
Mean values (s.d.) were shown as long as % was not indicated in the first column. Storage duration of sera, time period between blood drawing and BDNF assay.
a
Minor depressive disorder was diagnosed according to the criteria sets for further study in Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV).41
b
Minor depressive episode was defined as depression that meets the criteria for minor depressive disorder except that there had never been a major depressive episode or a dysthymic disorder.
c
One missing value.