Associated bone mineral density and obstructive sleep apnea in chronic obstructive pulmonary disease

Figures & data

Table 1 Patients characteristics

Characteristics	COPD without OSA (n=31)	COPD with OSA (n=35)	P-value
Age	71.6±8.5	71.5±8.6	0.951
Male, n (%)	29 (93.5)	33 (94.3)	0.348
BMI	23.8±3.4	24.9±4.3	0.958
Smoke, PKY	50.5±28.9	51.7±22.3	0.850
Pulmonary function test
FEV1/FVC	55.5±9.4	54.4±10.4	0.651
FEV1 (% predicted)	46.8±15.9	46.4±23.0	0.927
FVC (% predicted)	60.2±15.7	61.1±23.9	0.850
Incremental shuttle walk test, m	279.7±107.2	240.9±88.4	0.168
BMD
T-score (lumbar spine L2–4)	−1.27±1.14	−1.99±1.63	0.045
Medication
LABA, n (%)	29 (93.5)	32 (91.4)	0.999
ICS, n (%)	29 (93.5)	32 (91.4)	0.999
LAMA, n (%)	24 (77.4)	31 (88.6)	0.324
Theophyllines, n (%)	7 (22.6)	12 (34.3)	0.415
Oral corticosteroids, n (%)	11 (35.5)	7 (20)	0.178
PPI, n (%)	11 (35.5)	17 (48.6)	0.326

Note: Data are presented as mean ± standard deviation, or number (percentage).

Abbreviations: BMD, bone mineral density; BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; FVC, forced volume capacity; ICS, Inhaled corticosteroids; LABA, long-acting β₂ agonist; LAMA, long-acting muscarinic antagonist; OSA, obstructive sleep apnea; PKY, pack years; PPI, proton pump inhibitor.

Table 2 Polysomnographic results

	COPD without OSA (n=31)	COPD with OSA (n=35)	P-value
Total sleep time (minutes)	277.4±71.8	254.8±70.5	0.206
Sleep efficiency (%)	67.8±13.5	64.2±14.9	0.316
AHI events per hour	8.6±3.9	37.0±16.7	<0.001
ODI events per hour	4.4±3.6	21.1±15.4	<0.001
Average SaO2%	93.7±2.2	93.2±2.5	0.363
Lowest SaO2%	87.6±4.2	80.7±8.5	<0.001
Wake % TST	25.6±13.7	28.5±13.4	0.407
N1 % TST	18.8±12.1	20.5±9.9	0.525
N2 % TST	32.9±14.0	36.5±12.1	0.273
N3 % TST	10.8±11.0	6.5±9.1	0.091
REM % TST	11.7±6.8	8.0±7.1	0.032

Note: Data are presented as mean ± standard deviation.

Abbreviations: AHI, apnea–hypopnea index; COPD, chronic obstructive pulmonary disease; ODI, oxygen desaturation index; OSA, obstructive sleep apnea; REM, rapid eye movement; SaO₂, oxygen saturation; TST, total sleep time.

Table 3 Univariate analysis of variables associated with BMD at lumbar spine

Parameter	beta	Standard error	95% CI	P-value
Age	−0.013	0.021	−0.055 to 0.030	0.551
Sex	−0.290	0.761	−1.809 to 1.230	0.705
BMI	0.123	0.043	0.038 to 0.208	0.005
FEV1 %	0.025	0.009	0.008 to 0.043	0.005
ISWT, m	0.005	0.002	0.001 to 0.008	0.013
AHI	−0.021	0.009	−0.040 to −0.003	0.025
ODI	−0.026	0.013	−0.051 to −0.001	0.044
ICS	0.700	0.681	−0.661 to 2.061	0.308
Oral corticosteroids	−0.668	0.399	−1.466 to 0.130	0.099
PPI	−0.193	0.367	−0.926 to −0.540	0.600

Abbreviations: AHI, apnea–hypopnea index; BMD, bone mineral density; BMI, body mass index; CI, confidence interval; FEV₁, forced expiratory volume in 1 second; ICS, inhaled corticosteroids; ISWT, incremental shuttle walk test; ODI, oxygen desaturation index; PPI, proton pump inhibitor.

Table 4 Multivariate linear regression: factors associated with BMD at lumbar spine

Parameter	beta	Standard error	95% CI	P-value
BMI	0.133	0.039	0.054 to 0.211	0.001
FEV1 %	0.022	0.008	0.006 to 0.038	0.008
ODI	−0.031	0.011	−0.054 to −0.009	0.007

Abbreviations: BMD, bone mineral density; BMI, body mass index; CI, confidence interval; FEV₁, forced expiratory volume in 1 second; ODI, oxygen desaturation index.

Figure 1 Correlation analysis: an association between bone mineral density and apnea–hypopnea index.

Figure 2 Correlation analysis: an association between total lung capacity and oxygen desaturation index.

Figure 3 Correlation analysis: an association between total lung capacity and bone mineral density.