Machine learning approaches for screening the risk of obstructive sleep apnea in the Taiwan population based on body profile

Figures & data

Figure 1. Training Process with Grid Search Cross-Validation. Various machine learning models were trained using grid search cross-validation with subject-independent validation data for preventing overfitting. The overall accuracy of models for four age groups and sex groups was determined. The model exhibiting the highest performance was used to predict the testing data, and parameter importance was examined.

Abbreviations: LR, logistic regression; C: regularization values; kNN: k-nearest neighbor; NB: naive Bayes; var_smoothing: portion of the largest variance of all features; SVM: support vector machine; RF, random forest; tree_n: number of classification and regression trees; AHI: apnea–hypopnea index; LR+: positive likelihood ratio; LR−: negative likelihood ratio.

Table 1. Baseline characteristics of patients according to sex.

Categorical Variables	Male	Female	Total	P
Number (total)	7226	3165	10,391
Number (age ≥50/<50 years)	2985/4241	1750/1415	4735/5656
Age (years) ^a	48.01 ± 13.66	51.19 ± 14.05	48.97 ± 13.86	<0.01
BMI (kg/m^2) ^a	27.33 ± 4.67	25.79 ± 5.29	26.86 ± 4.92	<0.01
Neck circumference (cm) ^a	39.49 ± 4.13	34.34 ± 4.12	37.92 ± 4.76	<0.01
Waist circumference (cm) ^a	94.77 ± 11.73	85.41 ± 12.84	91.92 ± 12.83	<0.01
AHI (events/hour)	35.09 ± 26.62	19.37 ± 21.92	30.3 ± 26.29	<0.01
OSAS severity ^b				<0.01
AHI <5, n (%)	713 (9.87%)	990 (31.28%)	1703 (16.39%)
5≤ AHI <15, n (%)	1373 (19.00%)	834 (26.35%)	2207 (21.24%)
15≤ AHI <30, n (%)	1603 (22.18%)	626 (19.78%)	2229 (21.45%)
AHI ≥30, n (%)	3537 (48.95%)	715 (22.59%)	4252 (40.92%)

Data are expressed as the mean with standard deviation

BMI: body mass index; OSAS: obstructive sleep apnea syndrome

^aStudent’s t-test; ^b Chi-squared test

The P-value was calculated by the data between male and female groups.

Table 2. PSG results of patients according to sex.

Categorical Variables	Male aged <50 years	Male aged ≥50 years	Female aged <50 years	Female aged ≥50 years
Sleep efficiency (%)	80.04 ± 13.71 *	73.59 ± 15.01^*, $	79.96 ± 13.52 ^#	74.73 ± 14.75 ^#, $
WASO (min)	51.09 ± 42.85 ^&	75.71 ± 47.64 ^$	44.88 ± 39.41 ^#, &	65.01 ± 43.54 ^#, $
Sleep stage (% of SPT)
Wake	14.97 ± 12.61 ^*, &	22.18 ± 14.12 ^*, $	13.43 ± 11.94 ^#, &	19.44 ± 13.2 ^#, $
N1	12.75 ± 9.22 ^*, &	14.65 ± 10.14 ^*, $	8.98 ± 6.58 ^#, &	9.73 ± 7.09 ^#, $
N2	56.5 ± 14.55 ^*, &	52.19 ± 15.7 ^*, $	57.66 ± 13.86 ^&	56.81 ± 14.42 ^$
N3	4.22 ± 6.82 ^*, &	1.04 ± 3.06 ^*, $	7.08 ± 8.56 ^#, &	3.06 ± 5.67 ^#, $
REM	11.54 ± 6.04 ^*, &	9.94 ± 5.91^*, $	12.84 ± 6.38 ^#, &	10.95 ± 5.99 ^#, $
Sleep quality index (events/hour)
AHI	34.94 ± 28.31 ^&	35.29 ± 24.02 ^$	14.51 ± 21.44 ^#, &	23.31 ± 21.52 ^#, $
ODI-3%	32.88 ± 28.71 ^&	32.51 ± 24.11 ^$	12.60 ± 21.04 ^#, &	21.21 ± 21.11 ^#, $
Snoring index	257.39 ± 215.68 ^&	252.95 ± 219.35 ^$	156.38 ± 201.84 ^#, &	188.59 ± 211.27 ^#, $
Arousals index	25.51 ± 19.08 ^*, &	27.29 ± 16.78 ^*, $	16.18 ± 12.43 ^#, &	19.76 ± 13.01 ^#, $

Data are expressed as the mean with standard deviation

WASO: wake after sleep onset; SPT: sleep period time; N1: sleep stage one; N2: sleep stage two; N3: sleep stage three; REM: rapid-eye-movement stage; AHI: apnea–hypopnea index; ODI-3%: oxygen desaturation index for ≥ 3%.

*: the p value is <0.05 between younger and older male; ^#: the p value is <0.05 between younger and older female; ^&: the p value is <0.05 between male and female aged <50 years; ^$: the p value is <0.05 between male and female aged ≥50 years.

Table 3. Pearson’s correlation coefficients for PSG variables and anthropometric features in male.

Categorical Variables	Male aged <50 years (n = 4241)			Male aged ≥50 years (n = 2985)
	BMI (kg/m^2)	NC (cm)	WC (cm)	BMI (kg/m^2)	NC (cm)	WC (cm)
Sleep efficiency (%)	−0.06	−0.16*	−0.04*	0.09	0.04	−0.05*
WASO (min)	0.44*	0.73*	0.22*	−0.05	0.06	0.18*
Sleep stage (% of SPT)
Wake	0.13*	0.21*	0.06*	−0.04	0.01	0.05*
N1	0.38*	0.44*	0.16*	0.43*	0.47*	0.17*
N2	−0.19*	−0.29*	−0.09*	−0.31*	−0.37*	−0.17*
N3	−0.17*	−0.23*	−0.08*	−0.02	−0.05*	−0.01
REM	−0.15*	−0.14*	−0.06*	−0.08*	−0.05*	−0.04*
Sleep quality index (events/hour)
AHI	3.12*	2.99*	1.27*	2.84*	2.11*	1.06*
ODI-3%	3.21*	3.08*	1.32*	2.95*	2.14*	1.08*
Snoring index	12.33*	11.85*	5.31*	17.09*	13.17*	6.21*
Arousals index	1.21*	1.41*	0.51*	1.12*	0.93*	0.44*

BMI: body mass index; NC: neck circumference; WC: waist circumference; WASO: wake after sleep onset; SPT: sleep period time; N1: sleep stage one; N2: sleep stage two; N3: sleep stage three; REM: rapid-eye-movement stage; AHI: apnea–hypopnea index; ODI-3%: oxygen desaturation index for ≥ 3%.

*p < 0.05.

Table 4. Pearson’s correlation coefficients for PSG variables and anthropometric features in female.

Categorical Variables	Female aged <50 years (n = 1415)			Female aged ≥50 years (n = 1750)
	BMI (kg/m^2)	NC (cm)	WC (cm)	BMI (kg/m^2)	NC (cm)	WC (cm)
Sleep efficiency (%)	−0.03	0.07	−0.01	−0.02	−0.19*	−0.05
WASO (min)	0.39*	0.19	0.16*	−0.21	0.38	0.08
Sleep stage (% of SPT)
Wake	0.11*	0.04	0.04	−0.03	0.15	0.04
N1	0.16*	0.21*	0.07*	0.19*	0.24*	0.08*
N2	−0.11	−0.03	−0.05	−0.01	−0.19*	−0.04
N3	−0.11*	−0.22*	−0.04*	−0.08*	−0.12*	−0.03*
REM	−0.05	−0.01	−0.03*	−0.07*	−0.09*	−0.04*
Sleep quality index (events/hour)
AHI	1.89*	1.96*	0.82*	2.22*	2.01*	0.84*
ODI-3%	1.89*	1.93*	0.81*	2.28*	2.03*	0.85*
Snoring index	12.13*	14.34*	5.43*	13.37*	11.09*	5.41*
Arousals index	0.41*	0.59*	0.19*	0.49*	0.57*	0.19*

BMI: body mass index; NC: neck circumference; WC: waist circumference; WASO: wake after sleep onset; SPT: sleep period time; N1: sleep stage one; N2: sleep stage two; N3: sleep stage three; REM: rapid-eye-movement stage; AHI: apnea–hypopnea index; ODI-3%: oxygen desaturation index for ≥ 3%.

*p < 0.05.

Table 5. Comparison of the accuracy of screening moderate-to-severe and severe OSAS in grid search cross-validation of models based on groups.

Categorical Variables	LR	kNN	NB	SVM	RF
AHI ≥ 15/AHI < 15 -Acc
Group-1 (n = 2317/1075)	70.05 ± 4.61	83.02 ± 3.92	70.75 ± 4.58	71.23 ± 4.57	83.49 ± 3.88
Group-2 (n = 1814/574)	77.52 ± 5.17	82.21 ± 4.82	75.84 ± 5.27	77.52 ± 5.17	84.23 ± 4.38
Group-3 (n = 333/799)	81.56 ± 7.40	85.82 ± 6.87	79.43 ± 7.61	80.85 ± 7.47	90.07 ± 6.17
Group-4 (n = 749/651)	62.29 ± 7.63	78.86 ± 6.81	68.57 ± 7.44	65.71 ± 7.54	83.43 ± 5.18
Overall Acc	72.45 ± 2.70	82.47 ± 2.46	73.03 ± 1.82	73.41 ± 2.80	84.59 ± 2.35
AHI ≥ 30/AHI < 30 -Acc
Group-1 (n = 1587/1805)	64.86 ± 4.76	76.89 ± 4.31	67.22 ± 4.70	65.80 ± 4.73	80.19 ± 4.12
Group-2 (n = 1255/1133)	63.76 ± 5.74	71.81 ± 5.47	62.42 ± 5.77	55.37 ± 5.84	79.53 ± 5.03
Group-3 (n = 180/952)	80.85 ± 7.47	83.69 ± 7.15	82.98 ± 7.24	75.18 ± 7.97	85.82 ± 6.87
Group-4 (n = 403/997)	76.57 ± 6.98	85.14 ± 6.15	74.86 ± 7.11	78.86 ± 6.81	84.57 ± 6.22
Overall Acc	68.69 ± 2.92	76.88 ± 2.69	69.27 ± 2.91	66.28 ± 2.97	81.50 ± 2.32

Data are expressed as the mean and standard deviation

Group-1: male aged ≤50 years; Group-2: male aged >50 years; Group-3: female aged ≤50 years; Group-4: female aged >50 years; AHI: apnea–hypopnea index; Acc: accuracy; LR, logistic regression; kNN: k-nearest neighbors; NB: naive Bayes; SVM: support vector machine; RF, random forest

Table 6. Comparison of the area under the receiver operating characteristic curve (AUC) of grid search cross-validation outcomes by using various machine learning approaches.

Categorical Variables	LR	kNN	NB	SVM	RF
AHI ≥ 15/AHI < 15 -AUC
Group-1 (n = 2317/1075)	76.61 (72.97–80.35) *	89.35 (87.12–91.59)	76.61 (73.10–80.37) ^&	76.54 (72.91–80.34) ^$	88.73 (86.32–91.21) ^*, &, $
Group-2 (n = 1814/574)	74.69 (69.48–79.84) *	87.58 (84.44–90.37)	74.46 (69.11–79.71) ^&	70.02 (63.54–75.77) ^$	87.80 (84.14–91.18) ^*, &, $
Group-3 (n = 333/799)	84.29 (77.12–89.75) *	92.91 (88.86–95.95) ^#	84.41 (77.46–89.81) ^&	84.39 (77.25–89.99) ^$	97.88 (96.03–99.31) ^*, #, &, $
Group-4 (n = 749/651)	75.75 (69.19–81.33) *	86.89 (82.94–91.03) ^#	75.73 (69.21–81.65) ^&	75.96 (69.57–81.61) ^$	93.28 (90.43–95.93) ^*, #, &, $
AHI ≥ 30/AHI < 30 -AUC
Group-1 (n = 1587/1805)	76.18 (72.68–79.83) *	86.64 (84.05–89.13) ^#	76.63 (72.99–80.22) ^&	76.37 (72.86–79.93) ^$	96.80 (95.64–97.72) ^*, #, &, $
Group-2 (n = 1255/1133)	69.14 (63.46–73.97) *	81.56 (77.59–85.04) ^#	69.35 (63.68–74.28) ^&	69.28 (63.57–74.1) ^$	92.01 (89.28–94.46) ^*, #, &, $
Group-3 (n = 180/952)	83.45 (75.01–90.47) *	91.61 (87.84–94.79) ^#	83.11 (75.09–89.99) ^&	83.42 (75.34–90.24) ^$	95.20 (92.22–97.50) ^*, #, &, $
Group-4 (n = 403/997)	75.93 (68.81–82.19) *	92.25 (89.33–94.99)	78.04 (71.41–84.42) ^&	76.22 (69.08–83.05) ^$	94.38 (91.74–97.00) ^*, &, $

Group-1: male aged ≤50 years; Group-2: male aged >50 years; Group-3: female aged ≤50 years; Group-4: female aged >50 years; AHI: apnea–hypopnea index; Acc: accuracy; LR, logistic regression; kNN: k-nearest neighbors; NB: naive Bayes; SVM: support vector machine; RF, random forest; AUC: area under the curve.

Data are expressed as mean (95% CI)

Differences between the AUC of groups were all assessed using the DeLong’s test

*: the p value is <0.05 between RF and LR; ^#: the p value is <0.05 between RF and kNN; ^&: the p value is <0.05 between RF and NB; ^$: the p value is <0.05 between RF and SVM.

Figure 2. Area Under the Receiver Operating Characteristic Curve (AUC) of Grid Search Cross-Validation Outcomes by using Different Machine Learning Models.

Abbreviations: LR, logistic regression; kNN: k-nearest neighbor; NB: naive Bayes; SVM: support vector machine; RF, random forest; AHI: apnea–hypopnea index.

Table 7. Classification of the results of the age-dependent body profile in the random forest model for screening moderate-to-severe risk of OSAS for four groups.

Categorical Variables	Men aged ≤50 years	Men aged >50 years	Women aged ≤50 years	Women aged >50 years
Testing dataset (AHI ≥ 15/AHI < 15)	564/285	445 vs 152	72/211	187/163
Sensitivity, %	84.75 ± 3.23	93.26 ± 2.74	63.89 ± 10.99	77.54 ± 6.66
Specificity, %	59.65 ± 5.95	17.11 ± 5.62	80.57 ± 5.99	73.62 ± 7.46
Accuracy, %	76.33 ± 3.01	73.87 ± 3.72	76.33 ± 5.40	75.71 ± 4.84
LR+	2.10 ± 0.33	1.13 ± 0.09	3.29 ± 0.91	2.94 ± 0.69
LR−	0.26 ± 0.05	0.39 ± 0.15	0.45 ± 0.12	0.31 ± 0.08
AUC, % (95% CI)	80.86 (77.98–83.66)	68.57 (64.78–72.87)	76.47 (71.13–81.62)	78.79 (74.55–83.03)
Feature importance (100%)
BMI (%)	40.77%	41.50%	41.99%	39.84%
Neck circumference (%)	24.70%	22.61%	32.25%	23.58%
Waist circumference (%)	34.53%	35.89%	25.76%	36.58%

Data are expressed as the mean with standard deviation

AHI: apnea–hypopnea index; LR+: positive likelihood ratio; LR−: negative likelihood ratio; AUC: area under the curve.

Table 8. Classification results of the age-dependent body profile in random forest model for screening severe OSAS risk for four groups.

Categorical Variables	Men aged ≤50 years	Men aged >50 years	Women aged ≤50 years	Women aged >50 years
Testing dataset (AHI ≥ 30/AHI < 30)	402/447	293 vs 304	32 vs 251	100 vs 250
Sensitivity, %	71.89 ± 4.67	67.58 ± 5.69	40.62 ± 16.92	58.00 ± 10.29
Specificity, %	73.83 ± 4.34	66.78 ± 5.61	89.64 ± 4.45	89.20 ± 4.52
Accuracy, %	72.91 ± 3.13	67.17 ± 3.93	84.10 ± 4.79	80.29 ± 4.56
LR+	2.75 ± 0.43	2.03 ± 0.33	3.92 ± 1.67	5.37 ± 1.75
LR−	0.38 ± 0.06	0.49 ± 0.09	0.66 ± 0.16	0.47 ± 0.10
AUC, % (95% CI)	77.37 (74.35–80.10)	68.82 (65.21–72.42)	81.24 (73.98–87.59)	78.01 (73.02–82.69)
Feature importance (100%)
BMI (%)	40.72%	38.98%	38.11%	38.84%
Neck circumference (%)	24.87%	24.13%	36.36%	26.57%
Waist circumference (%)	34.41%	36.89%	25.53%	34.59%

Data are expressed as the mean with standard deviation

AHI: apnea–hypopnea index; LR+: positive likelihood ratio; LR−: negative likelihood ratio; AUC: area under the curve.