Depressive Symptoms Are Associated with Self-Reported Physical Limitations That Are Activity Dependent in a Cross-Sectional Analysis of Subjects with Chronic Obstructive Pulmonary Disease

Figures & data

Figure 1. Study selection criteria. The 2007–2012 NHANES surveys included 30,442 individuals from across the USA. From this cohort, our study included the 775 subjects age 40–79 who had valid responses to all questions on the PHQ-9, had obstructive lung disease, responded to at least one of the physical function questions, and had history of regular smoking.

Table 1. Demographics by the presence of depressive symptoms.

	No depression (n = 700)	Depressive symptoms (n = 75)
Age in years (IQR)	67 (62, 73)	55 (49, 64)
Male sex (%)	488 (70)	34 (45)
Current smokers (%)	280 (40)	53 (71)
Age started smoking regularly (IQR)*	17 (15, 19)	15 (14, 18)
Age quitters stopped smoking regularly (IQR)*	46 (35, 57)	44 (38, 57)
Ethnicity
Caucasian (%)	445 (64)	45 (60)
Mexican American (%)	40 (6)	5 (7)
Other Hispanic (%)	49 (7)	6 (8)
Non-Hispanic Black (%)	139 (20)	17 (23)
Other race (%)	27 (4)	2 (3)
Income < 2 × Poverty (%)*	313 (48)	58 (87)
Insured (%)	632 (90)	60 (80)
PHQ-score (IQR)	1 (0, 3)	13 (11, 17)
FEV1 % predicted (IQR)*	80 (66, 92)	71 (56, 85)
BMI (IQR)*	28 (24, 31)	27 (23, 32)
Co-morbidities
Obese (%)*	229 (33)	27 (36)
CAD (%)*	68 (10)	5 (7)
CHF (%)*	49 (7)	5 (7)
Anemia (%)*	27 (4)	4 (5)
Liver disease (%)*	24 (3)	8 (11)
1 co-morbidity**	315 (45)	39 (52)
>1 co-morbidity (%)**	74 (11)	8 (11)
>2 co-morbidity (%)**	8 (1)	2 (3)

Note: Median (IQR) or number of subjects (%) reported for each demographic statistic. *Indicates at least one missing observation. Median number of subjects for all demographics reported here was 698 (695, 700) for subjects without depression and 75 (75, 75) for patients with depressive symptoms. **In calculating the number of co-morbidities for each patient, patients missing obesity, CAD, CHF, anemia, or liver disease data were assumed not to have the co-morbidity in question.

Table 2. IPTW sample demographics by the presence of depressive symptoms.

	No depression (n = 649)	Depressive symptoms (n = 63)
Age in years (IQR)	67 (61, 72)	69 (60, 73)
Male sex (%)	431 (66)	33 (52)
Current smokers (%)	281 (43)	23 (36)
Caucasian (%)	421 (65)	27 (43)
Income < 2 × Poverty (%)	337 (52)	33 (52)
FEV1 % predicted (IQR)	79 (65, 91)	81 (64, 87)
BMI (IQR)*	28 (24, 32)	25 (22, 31)
Co-morbidities
1 co-morbidity (%)**	228 (35)	17 (27)
>1 co-morbidity (%)**	68 (10)	5 (9)
>2 co-morbidity (%)**	7 (1)	4 (6)

Note: Median (IQR) or number of subjects (%) reported for each demographic statistic. *For BMI, the number of subjects without depression symptoms was 648. **In calculating the number of co-morbidities for each patient, patients missing obesity, CAD, CHF, anemia, or liver disease data were assumed not to have the co-morbidity in question.

Figure 2. Self-report of difficulty with physical activities by the presence of depressive symptoms. COPD patients with depressive symptoms were more likely to report difficulty with the physical activities walking a quarter mile, walking up 10 stairs, and walking between rooms than non-depressed COPD patients.

Table 3. Unadjusted odds ratio estimates for the association between demographic variables and self-reported difficulty with physical activity.

	Walking a quarter mile (n = 680)	Odds ratio for any difficulty Walking up 10 stairs (n = 686)	Walking between rooms (n = 775)
Age in years	0.98 (0.96, 1.00)	0.96 (0.944, 0.98)	0.96 (0.93, 0.99)
Female sex	1.45 (1.02, 2.05)	1.72 (1.18, 2.52)	1.95 (1.12, 3.38)
Current smoker	1.87 (1.34, 2.62)	1.80 (1.25, 2.61)	1.65 (0.95, 2.87)
Caucasian	1.20 (0.85, 1.70)	0.97 (0.66, 1.42)	0.80 (0.46, 1.39)
Income < 2 × Poverty*	2.34 (1.57, 3.19)	2.90 (1.99, 4.36)	4.16 (2.05, 8.45)
Insurance status	1.07 (0.62, 1.87)	0.89 (0.49, 1.60)	1.57 (0.55, 4.47)
FEV1 % predicted*	0.97 (0.97, 0.98)	0.97 (0.96, 0.98)	0.98 (0.97, 1.00)
Number of co-morbidities	1.73 (1.37, 2.19)	1.50 (1.17, 1.92)	1.78 (1.27, 2.49)

Note: OR (95% CI) are provided for predictors of self-reported difficulty with three physical activities. *For covariate income < 2 × poverty limit, the number of patients for walking a quarter mile, walking up 10 stairs, and walking between rooms was 630, 634, and 716, respectively. For covariate FEV1 % predicted, the number of patients for walking a quarter mile, walking up 10 stairs, and walking between rooms was 678, 684, and 773, respectively.

Table 4. Odds ratio estimates for depressive symptoms as a predictor of self-reported difficulty with physical activity.

	Univariable model	Multivariable model	Multivariable IPTW model
Walking a quarter mile	2.74 (1.62, 4.67)	2.03 (1.06, 3.88)	2.82 (1.49, 5.33)
Walking up 10 stairs	4.88 (2.85, 8.35)	3.40 (1.77, 6.50)	5.01 (2.65, 9.48)
Walking between rooms	6.26 (3.37, 11.62)	4.92 (2.29, 10.60)	5.42 (2.55, 11.50)

Note: OR (95% CI) are provided for depressive symptoms as a predictor of self-reported difficulty with three physical activities. Multivariable modeling includes PHQ-score ≥10, gender, age, FEV1 % predicted, poverty status, smoking status, and number of co-morbidities. Median number of subjects to predict self-reported difficulty walking a quarter mile, walking up 10 stairs, and walking between rooms was 628 (625, 654), 632 (629, 659), and 714 (713, 745), respectively.