3.1. Clinical characteristic of patients with COPD with depression and non-depression
As shown in Table 1, Race (P = 0.008) and Hypertension (P = 0.014) showed statistically significant differences between patients with depression and those without depression. Gender (P = 0.971), Mean age (56.59 VS 53.64,P = 0.164), Body mass index (82.9kg/m2 VS 88.18kg.m2,P = 0.169), Average leukocyte level (7.85*109/L VS 7.54* 109/L, P = 0.410), lymphocyte (2.29*109/L VS 2.15*109/L, P = 0.607), Platelet average (275.68*109/L VS 276.76*109/L, P = 0.911), The mean levels of neutrophils (4.68*109/L VS 4.59*109/L, P = 0.700) and Monocytes (0.59*109/L VS 0.54*109/L, P = 0.059). There were no statistically significant differences between Participants with and without depression in Education level (P = 0.032), Smoking (P = 0.771), Diabetes (P = 0.155) and sleep disorders (P = 0.186).
Table 1
The characteristics of COPD patients with and without depression
Parameters | Total | Depression |
| N = 494 | NO(n = 420) | YES(n = 74) | P Value |
Sex | | | | 0.971 |
Male | 226(45.75%) | 192(45.71%) | 34(45.95%) | |
Female | 268(54.25%) | 228(54.29%) | 40(54.05%) | |
Age(N.%) | 56.14 + 16.80 | 56.59 ± 17.3 | 53.64 ± 13.43 | 0.164 |
Male | - | 89(41.2%) | 11(32.35%) | |
Female | - | 127(58.8%) | 23(67.65%) | |
Race | | | | 0.008 |
Mexican American | 46(9.31%) | 41(9.76%) | 5(6.76%) | |
Other Hispanic | 34(6.88) | 25(5.95%) | 9(12.16%) | |
Non-Hispanic Black | 316(63.97%) | 279(66.43%) | 37(50%) | |
BMI | 83.70 ± 22.86 | 82.90 ± 22.57 | 88.18 ± 24.15 | 0.069 |
Education | | | | 0.454 |
Below high school | 162(32.79%) | 132(31.43%) | 30(40.54%) | |
College school | 120(24.29%) | 103(24.52%) | 17(22.97%) | |
Beyond College school | 211(42.71%) | 184(43.81%) | 27(36.49%) | |
Marital status | | | | 0.106 |
Marital/living with partner | 272(55.06%) | 231(55%) | 41(55.41%) | |
Widow/never married | 125(25.30%) | 112(26.67%) | 13(17.57%) | |
Divorced/separated | 97(19.64%) | 77(18.33%) | 20(27.03%) | |
Hypertension | | | | 0.014 |
YES | 229(45.75%) | 185(44.05%) | 44(59.46%) | |
NO | 265(53.64%) | 235(55.95%) | 30(40.54%) | |
Diabetes | | | | 0.155 |
YES | 88(17.81%) | 72(17.14%) | 16(21.62%) | |
NO | 393(79.55%) | 339(80.71%) | 54(72.97%) | |
Alcohol | | | | 0.663 |
YES | 350(70.85%) | 296(70.48%) | 54(72.97%) | |
NO | 144(29.15%) | 124(29.52%) | 20(27.03%) | |
Sleep disorders | | | | 0.186 |
YES | 75(15.18%) | 60(14.29%) | 15(20.27%) | |
NO | 419(84.98%) | 360(85.71%) | 59(79.73%) | |
Smoking | | | | 0.771 |
YES | 340(68.83%) | 288(68.57%) | 30(40.54%) | |
NO | 154(31.71%) | 132(31.43%) | 22(29.73%) | |
CRP,mg/dL | 0.64 + 1.24 | 0.60 ± 1.09 | 0.88 ± 1.88 | 0.078 |
WBC,10^9cells/L | 7.80 + 2.92 | 7.85 ± 3.03 | 7.54 ± 2.18 | 0.410 |
LYM,10^9cells/L | 2.27 + 2.15 | 2.29 ± 2.30 | 2.15 ± 0.79 | 0.607 |
MONO,10^9cells/L | 0.58 + 0.21 | 0.59 ± 0.21 | 0.54 ± 0.16 | 0.059 |
NEUT,10^9cells/L | 4.67 + 1.73 | 4.68 ± 1.71 | 4.59 ± 1.85 | 0.700 |
PLT,10^9cells/L | 275.84 + 74.63 | 275.68 ± 73.43 | 276.76 ± 81.81 | 0.911 |
COPD: chronic obstructive pulmonary disease, WBC: white blood cell, MONO: monocyte, NEUT: neutrophil, PLT: platelet, LYM: lymphocyte |
3.2. Characteristic analysis of the Training Set and Testing Set
The subjects were randomly divided into a training set and a test set (7:3). In the training group, the age of training concentration depression was younger (p = 0.015), the prevalence of hypertension was higher (69.09% VS 47.93%.p = 0.004), and the monocyte count was lower (p = 0.004)(Table 2).
Table 2
The equilibrium test of the training set and testing set.
Parameters | Training set (n = 345) | P Value | Testing set (n = 149) | P Value |
| Depression(n = 55) | Non-depression(n = 290) | | Depression(n = 19) | Non-depression(n = 130) | |
Sex | | | 0.097 | | | 0.006 |
Male | 25(45.45%) | 167(57.59%) | | 9(47.37%) | 25(19.23%) | |
Female | 30(54.55%) | 123(42.41%) | | 13(68.42%) | 105(80.77%) | |
Age | 52.73 + 12.84 | 58.64 + 16.51 | 0.012 | 53.64 ± 13.43 | | 0.219 |
Race | | | 0.011 | | | 0.364 |
Mexican American | 3(5.45%) | 22(7.59%) | | 2(10.53%) | 19(14.62%) | |
Other Hispanic | 4(7.27%) | 18(6.21%) | | 5(26.32%) | 7(5.38%) | |
Non-Hispanic Black | 28(50.91%) | 198(68.28%) | | 9(47.37%) | 81(62.3%) | |
BMI | 85.15 + 21.42 | 84.78 + 22.96 | | 76.23 + 25.54 | 78.72 + 21.15 | 0.471 |
Education | | | 0.657 | | | 0.672 |
Below high school | 24(43.64%) | 103(35.52%) | | 6(31.58%) | 29(22.31%) | |
College school | 12(21.82%) | 65(22.41%) | | 5(26.32%) | 38(29.23%) | |
Beyond College school | 19(34.55%) | 121(41.72%) | | 8(42.11%) | 63(48.46%) | |
Marital status | | | 0.208 | | | 0.501 |
Marital/living with partner | 28(50.91%) | 154(53.1%) | | 13(68.42%) | 77(59.23%) | |
Widow/never married | 10(18.18%) | 75(25.86%) | | 3(15.79%) | 37(28.46%) | |
Divorce/separated | 17(30.91%) | 61(21.03%) | | 3(15.79%) | 16(12.31%) | |
Hypertension | | | 0.004 | | | 0.745 |
YES | 38(69.09%) | 139(47.93%) | | 6(31.58%) | 46(35.38%) | |
NO | 17(30.91%) | 151(52.07%) | | 13(68.42%) | 84(64.62%) | |
Diabetes | | | 0.087 | | | 0.655 |
YES | 15(27.27%) | 57(19.66%) | | 1(5.26%) | 114(87.69%) | |
NO | 36(65.45%) | 225(77.59%) | | 18(94.74%) | 15(11.54%) | |
Alcohol | | | 0.792 | | | 0.374 |
YES | 41(25.45%) | 221(76.21%) | | 13(68.42%) | 75(57.6%) | |
NO | 14(74.55%) | 69(23.79%) | | 6(31.58%) | 55(42.31%) | |
Sleep disorders | | | 0.915 | | | 0.007 |
YES | 10(18.18%) | 51(17.59%) | | 5(26.32%) | 9(6.92%) | |
NO | 45(81.82%) | 239(82.41%) | | 14(73.68%) | 121(93.08%) | |
Smoking | | | 0.445 | | | 0.160 |
YES | 49(89.09%) | 247(85.17%) | | 3(84.21%) | 41(31.54%) | |
NO | 6(10.91%) | 43(14.83%) | | 16(84.21%) | 89(68.46%) | |
CRP,mg/dL | 1.01 + 2.12 | 0.64 ± 1.22 | 0.072 | 0.47 ± 0.52 | 0.51 ± 0.70 | 0.813 |
WBC,10^9cells/L | 7.57 + 2.27 | 8.06 + 3.39 | 0.308 | 7.45 + 1.93 | 7.35 + 1.84 | 0.839 |
LYM,10^9cells/L | 2.09 + 0.78 | 2.36 ± 2.71 | 0.465 | 2.15 + 0.74 | 2.13 + 0.71 | 0.263 |
MONO,10^9cells/L | 0.53 + 0.16 | 0.62 + 0.22 | 0.012 | 0.57 ± 0.18 | 0.53 ± 0.18 | 0.575 |
NEUT,10^9cells/L | 4.69 + 1.89 | 4.8 ± 1.79 | 0.703 | 4.28 + 1.72 | 4.40 ± 1.47 | 0.750 |
PLT,10^9cells/L | 281.42 + 88.52 | 273.27 ± 72.06 | 0.467 | 262.24 + 55.65 | 281.36 ± 76.56 | 0.323 |
COPD: chronic obstructive pulmonary disease, WBC: white blood cell, MONO: monocyte, NEUT: neutrophil, PLT: platelet, LYM: lymphocyte |
3.3.Nomogram model Prediction and construction
LASSO regression analysis was performed to identify ten predictors and calculate the scoring formula:0.0053*BMI-0.49088*HYERTENSION:0 + 0.01342*HYERTENSION:1-1.39336*MONO + 0.12963*CRP + 0.05156*SEX: 0–0.01982*AGE + 0.56148*RACE:4 + 0.01897*EDU:1-0.051*MARRIAGE:2 + 0.20255*MARRIAGE:3-0.01676*DIABETES: 2.
We further carried out multivariate logistic regression analysis and generated a prediction model. The results of multivariate logistic regression analysis are shown in Table 3. Ten variables screened by LASSO regression were incorporated into multiple logistic regression model to establish a prediction model. The results showed that four variables were statistically significant in predicting the risk of depression secondary to COPD. hypertension(Odds Ratio [OR],0.433; 95% confidence interval[CI],0.206–0.914; P = 0.028),MONO (OR, 0.071; 95% CI, 0.011 to 0.437; P = 0.004), CRP (OR,1.269; 95% CI, 1.047 to 1.538; P = 0.015) and Age (OR,0.970; 95% CI, 0.947 to 0.992; P = 0.009). So the four indicators are included in the nomogram.
Table 3
Predictors of depression in COPD patients by multivariate logistic regression analysis.
Variable | β | S.E | Wald | P | OR | lower | upper |
Hypertension | 0.836 | 0.381 | 4.821 | 0.028 | 0.433 | 0.206 | 0.914 |
MONO | −2.652 | 0.930 | 8.124 | 0.004 | 0.071 | 0.011 | 0.437 |
CRP | 0.238 | 0.098 | 5.911 | 0.015 | 1.269 | 1.047 | 1.538 |
Age | 0.031 | 0.012 | 6.914 | 0.009 | 0.970 | 0.947 | 0.992 |
Abbreviation: |
MONO,Monocyte cell ; CRP, C-reactive protein |
Based on the four screened variables, we constructed Nomogram to predict the likelihood of depression in COPD patients. The point total is calculated from the sum of the points assigned to each variable. The higher the point, the higher depression prevalence rate in COPD,Combined with this model, the risk of depression is relatively good(Fig. 3).
3.4.Validation of the Predicative Value via the Testing Set.
ROC curves of training set and test set are shown in Fig. 3. The AUC value of the prediction model was 0.774 in the training set and 0.713 in the test set which indicates average and good performance(Fig. 4).
3.5. the calibration of the model in the training set and the testing set
Calibration curve had be drawn as evaluating the calibration of the model. The calibration curve accounted for the relationship between the depression risk predicted by the model and the depression risk observed in the training cohort. The calibration curve of the nomogram for predicting depression risk in COPD patients made clear that relative good agreement both the training and validation datasets (Figs. 5A and B). To summarize the above verification results, the nomogram of the model has relative good predictive ability.
3.6.DCA of the prediction model in the training set and the testing set
DCA was used to evaluate the clinical efficacy of the prediction model. The DCA curve is plotted using the predicted depression probabilities of the model and validation group and the actual occurrence of depression probabilities. The DCA curves of the two groups are revealed in Fig. 6A and B.The prediction probability threshold in the training and validation was between 12.5%-60% and 12%-30%, and validation sets was between 0-2.5% and 0–2%.The smaller the threshold, the better the net benefit.