Of 127 community-dwelling residents from the northern coastal area of Taiwan, nine were excluded as subjects for incompletely answering the TDQ, AD8 or MINI. A total of 118 residents were thus enrolled. Based on MINI diagnoses, of those with current MDD 33.3% were widowed and 22.2% were divorced, whereas only 10.7% and 6.8% of those without current MDD (p < 0.05) were widowed and divorced, respectively. Both TDQ scores (25.56 ± 10.90 versus 11.05 ± 9.79, p < 0.001) and AD8 scores (4.00 ± 2.45 versus 1.94 ± 2.09, p < 0.01) were higher in the group with current MDD. A higher percentage risk of suicide was identified in people with current MDD (55.6% versus 0%). The group comparison revealed no difference in age, sex, years of education, income level or cognition status in terms of MMSE score. (Table 1)
Table 1
Basic information and questionnaire scoring of people with and without current MDD by MINI diagnosis
Variables | Current MDD | No current MDD | p |
Number | 9 | 109 | |
Age | 63.22 ± 2.68 | 64.94 ± 5.12 | .322 |
Sex (female) | 8 (88.9%) | 65 (59.6%) | .150 |
Years of school education | 7.78 ± 3.63 | 10.19 ± 4.30 | .108 |
Marital status | | | .025* |
Married | 4 (44.4%) | 85 (82.5%) | |
Divorced | 2 (22.2%) | 7 (6.8%) | |
Widowed | 3 (33.3%) | 11 (10.7%) | |
Annual income level (103 USD) | | | .729 |
< 10 | 3 (33.3%) | 29 (29.3%) | |
10–30 | 3 (33.3%) | 39 (39.4%) | |
30–60 | 1 (11.1%) | 22 (22.2%) | |
> 60 | 1 (11.1%) | 4 (4.0%) | |
Concealed | 1 (11.1%) | 5 (5.1%) | |
TDQ score | | | |
TDQ ≥ 19 | 8 (88.9%) | 24 (22.0%) | < .001* |
Total | 25.56 ± 10.90 | 11.05 ± 9.79 | < .001* |
MINI-suicide: | | | < .001* |
High risk | 5 (55.6%) | 0 (0.0%) | |
Low risk | 3 (33.3%) | 7 (6.4%) | |
No risk | 1 (11.1%) | 102 (93.65) | |
AD8 score | 4.00 ± 2.45 | 1.94 ± 2.09 | .006* |
MMSE score | 27.56 ± 1.59 | 28.12 ± 2.05 | .427 |
* Statistic significant at 0.05 level. MINI, Mini-International Neuropsychiatric Interview. MDD, Major depressive disorder. TDQ, Taiwanese Depression Questionnaire. MMSE, Mini-mental state examination. |
Spearman’s rho statistics were used to evaluate correlations among TDQ, age, years of education, income level, AD8 score, MMSE score, PSQI score and SF-36 score. Statistics revealed a weak correlation between TDQ and AD8 scores with a correlation coefficient of 0.386 at a significance of p < 0.01 (Table 2). Depressive tendency slightly increased with subjective cognitive complaints. The depressive score on the TDQ was also moderately correlated with sleep quality in terms of PSQI (correlation coefficient 0.561, p < 0.001), quality of life with respect to general health (correlation coefficient − 0.564, p < 0.001), vitality (correlation coefficient − 0.688, p < 0.001) and mental health, per the SF-36 questionnaire (correlation coefficient − 0.603, p < 0.001). These results suggest that sleeping quality and quality of life worsen as depressive traits increase.
Table 2
Correlation analysis by Spearman’s rho statistics
| TDQ | Age | Education year | Annual income | AD8 | MMSE | PQSI | SF-36 |
PF | RP | BP | GH | VT | SF | RE | MH |
TDQ | 1.000 | | | | | | | | | | | | | | |
Age | − .064 | 1.000 | | | | | | | | | | | | | |
Education year | − .026 | − .273** | 1.000 | | | | | | | | | | | | |
Annual income | − .239* | .016 | .345** | 1.000 | | | | | | | | | | | |
AD8 | .386** | − .124 | − .080 | − .066 | 1.000 | | | | | | | | | | |
MMSE | − .076 | − .324** | .443** | .109 | − .107 | 1.000 | | | | | | | | | |
PSQI | .561** | .030 | .118 | − .134 | .391** | − .032 | 1.000 | | | | | | | | |
SF-36 | PF | − .389** | .014 | .209 | .137 | − .321** | .172 | − .325** | 1.000 | | | | | | | |
RP | − .402** | .046 | .100 | .147 | − .385** | .047 | − .313** | .623** | 1.000 | | | | | | |
BP | − .311** | − .082 | .103 | .038 | − .276** | .117 | − .297** | .550** | .575** | 1.000 | | | | | |
GH | − .546** | − .018 | .179 | .279** | − .335** | .216* | − .474** | .465** | .468** | .551** | 1.000 | | | | |
VT | − .688** | − .013 | .093 | .124 | − .374** | .117 | − .482** | .490** | .424** | .365** | .585** | 1.000 | | | |
SF | − .413** | .155 | − .145 | − .020 | − .194** | − .054 | − .387** | .461** | .391** | .390** | .389** | .450** | 1.000 | | |
RE | − .465** | .124 | .042 | − .014 | − .369** | .070 | − .384** | .394** | .539** | .271** | .334** | .425** | .292** | 1.000 | |
MH | − .603** | .133 | − .015 | .122 | − .391** | .020 | − .424** | .378** | .397** | .199** | .496** | .703** | .413** | .460** | 1.000 |
Correlations between variables were analyzed by Spearman's rank correlation coefficient (Spearman's rho, ρ). * Correlation was significant at 0.05 level (2-tailed). ** Correlation was significant at 0.01 level (2-tailed). TDQ, Taiwanese Depression Questionnaire. MMSE, Mini-mental state examination. PQSI, Pittsburgh Sleep Quality Index. SF-36, Short Form (36-item) Health Survey. PF, physical functioning. RP, physical role functioning. BP, body pain. GH, general health. VT, vitality. SF, social role functioning. RE, emotional role functioning. MH, mental health. |
In the logistic regression model for the MINI diagnosis of current MDD, AD8 and TDQ scores were both included as variables. TDQ score alone and AD8 score alone had 1.127 (p = 0.001) and 1.463 (p = 0.012) folds of odds of indicating current depression in MINI respectively (Table 3, models 1 and 2). Accounting for whether someone is elderly (age ≥ 65) and their sex, TDQ score significantly influenced the diagnosis of depression (Table 3, model 3). When sleep quality in terms of PSQI and objective cognitive assessment in terms of MMSE are considered along with old age and sex, both TDQ and AD8 scores significantly affected the likelihood of a depressive disorder (odds ratios OR 1.154, p = 0.003 and OR 1.769, p = 0.018, Table 3, model 4).
Table 3
Logistic regression model to determine MINI diagnosis of current MDD
| Model 1 | | Model 2 | | Model 3 | | Model 4 | |
| B | SE | p | OR | | B | SE | p | OR | | B | SE | p | OR | | B | SE | p | OR | |
TDQ | .119 | .036 | .001* | 1.127 | | | | | | | .109 | .038 | .004* | 1.115 | | .143 | .048 | .003* | 1.154 | |
AD8 | | | | | | .381 | .151 | .012* | 1.463 | | .399 | .205 | .051 | 1.490 | | .570 | .241 | .018* | 1.769 | |
Sex | | | | | | | | | | | 2.001 | 1.230 | .104 | 7.397 | | 2.436 | 1.456 | .094 | 11.433 | |
Age ≥ 65 | | | | | | | | | | | .207 | .854 | .809 | 1.229 | | .066 | 1.123 | .953 | 1.068 | |
MMSE | | | | | | | | | | | | | | | | − .086 | .234 | .714 | .918 | |
PSQI | | | | | | | | | | | | | | | | − .068 | .125 | .584 | .934 | |
* Statistic significant at 0.05 level. MINI, Mini-International Neuropsychiatric Interview. MDD, Major depressive disorder. TDQ, Taiwanese Depression Questionnaire. MMSE, Mini-mental state examination. SE, standard error. OR, odds ratio. |
The ROC curve was used to evaluate the performance of self-reported questionnaires in predicting a diagnosis of major depression. The AUC was 0.835 for the TDQ score (p = 0.001) and 0.751 for the AD8 score (p = 0.013). An AUC over 0.5 was regarded as indicating that target values could be effectively classified. When using the linear combination of TDQ and AD8, the sum of TDQ score and four times the AD8 score predicted a MINI diagnosis of major depression with an AUC of 0.887 (p < 0.001) (Fig. 3-A). Calculating Youden’s J statistics as [(sensitivity + specificity) – 1] yielded the best cutoffs of TDQ for predicting MDD, which were identical to that originally proposed for clinical use: a TDQ score of 19 with a sensitivity 0.889, a specificity of 0.780, a positive predictive value of 88.9% and a negative predictive value of 77.3%. A linearly combined TDQ and AD8 score of ≥ 31 was feasibly predicted MDD diagnosis by MINI for community-dwelling people, with a sensitivity of 1.000, a specificity of 0.789, a positive predictive value of 100% and a negative predictive value of 77.1%.
Owing to the possibility of atypical presentations, such as subjective cognitive complaints in elderly people with major depression, enrollees were separated into groups of age ≥ 65 and age 50–65, to examine whether age influenced likelihood of major depression. In the elderly group (Fig, 3-B), prediction by TDQ score or AD8 score alone was unsatisfactory, yielding AUCs of only 0.780 (p = 0.063) and 0.627 (p = 0.398) respectively, and failing to reach statistical significance. The sum of the TDQ score and four times the AD8 score, however, offered much improved predictive performance, with an AUC of 0.875 (p = 0.013). In the group with age 50–65 (Fig. 1-C), the TDQ score, AD8 score and their linear combination were less predictive, but the linear combination remained the strongest predictor; the AUC values were 0.892 (p = 0.004), 0.804 (p = 0.026), and 0.918 (p = 0.002) respectively.
To classify people with and without major depression, a basic machine learning algorithm with decision tree learning was used to analyze the effects of such variables as age, sex, education year, level of annual income, marital status, TDQ score, AD8 score, and the sum of TDQ and four times the AD8 score. The model thus obtained had two levels and four nodes. The linear combination of TDQ score + 4*AD8 score was at level 1, and a value of less than 29 at node 1 indicated no current MDD while a value of over 29 at node 2 indicated current MDD. The second level came from node 2 by sex; the female gender at node 3 favored current MDD whereas the male gender favored no current MDD (Fig. 2).