The impact of SHS exposure on health status and exacerbations among patients with COPD

Figures & data

Table 1 Baseline characteristics of the nonsmoking FLOW cohort by SHS exposure status (n = 809)

Characteristic	No SHS exposure (n = 445)	Low level SHS exposure (n = 200)	High level SHS exposure (n = 164)	P value for comparison
Age (years)	58 (6.3)	59 (6.1)	59 (5.9)	0.31
Sex (female)	269 (61%)	106 (53%)	86 (52%)	0.088
White, non-Hispanic	304 (68%)	131 (66%)	106 (65%)	0.62
Smoking history
Never smoked	100 (23%)	37 (19%)	28 (17%)	0.25
Ex-smoker	348 (78%)	163 (82%)	136 (83%)
Educational attainment				0.014
High school or less	111 (25%)	46 (23%)	62 (38%)
Some college	183 (41%)	88 (44%)	61 (37%)
College or graduate degree	151 (34%)	66 (33%)	41 (25%)
Married or cohabiting	286 (64%)	130 (65%)	113 (69%)	0.56
COPD severity score	10.1 (6.1)	11 .0 (6.5)	10.5 (5.6)	0.71
BODE score	3.0 (2.4)	2.9 (2.5)	2.6 (2.2)	0.23
FEV1 % predicted	62 (23)	62 (24)	65 (22)	0.32

Notes: Results are mean (sd) for age, COPD severity score, and BODE score; n (%) for all others – column proportions are reported.

Abbreviations: COPD, chronic obstructive pulmonary disease; FEV₁ forced expiratory volume in one second; FLOW, Function, Living, Outcomes, and Work study; SHS, secondhand smoke.

Table 2 SHS exposure during the past seven days among adults with COPD

Group of subjects	Median (hours)	25th–75th IQR (hours)
All subjects (n = 809)	0	0–4.0
Subgroup with any SHS exposure
Entire subgroup (n = 364)	1.0	0.5–3.0
Lower level exposure (n = 200)*	0.7	0.3 to 1.0
Higher level exposure (n = 164)	4.0	2.0–6.0

Notes: *SHS exposure was assessed using a validated survey instrument that assessed duration of SHS exposure (hours) during the past seven days in a variety of microenvironments. The hours of SHS exposure during the past seven days in each microenvironments were summed to calculate the total. Lower level and higher level were divided at the median among those with any exposure.

Abbreviations: COPD, chronic obstructive pulmonary disease; IQR, interquartile range; SHS, secondhand smoke.

Table 3 Impact of SHS exposure on health status in COPD

SHS exposure category*	Health status outcome†
	Physical health status	Disease-specific HRQL	Submaximal exercise performance
	Mean points (95% CI)	Mean points (95% CI)	Mean feet walked in six minutes (95% CI)
None (n = 838)	0 (referent)	0 (referent)	0 (referent)
Lower level SHS exposure (n = 200)	0.007 (−1.56 to 1.57) P = 0.99	0.36 (−0.21 to 0.93) P = 0.22	−0.62 (−49 to 47) P = 0.98
Higher level SHS exposure (n = 164)	−1.78 (−3.48 to −0.074) P = 0.041‡‡	0.63 (0.016 to 1.25) P = 0.04‡‡	−50 (−102 to 1.9) P = 0.059‡‡

Notes: Multivariable linear regression controlling for age, sex, race, educational attainment, smoking history, COPD severity score, and BODE score. Results are mean change in health status outcome variable for lower level HS exposure vs none; higher level SHS exposure vs none;

* Based on validated survey instrument that assessed duration of SHS exposure (hours) during the past seven days in a variety of microenvironments. Lower level and higher level were divided at the median among those with any exposure;

^† Physical health status was assessed using the SF-12 Physical Component Summary Score; Disease-specific health-related quality of life with the Airways Questionnaire 20-Revised; Submaximal exercise performance with the Six-Minute Walk Test;

^‡‡ p < 0.05 in linear regression analysis using backwards selection (to eliminate covariates with p value ≥0.10).

Abbreviations: CI, confidence interval; COPD, chronic obstructive pulmonary disease; HRQL, health-related quality of life; SHS, secondhand smoke.

Table 4 Prospective impact of SHS exposure on emergency health care utilization for COPD

SHS exposure category*	Emergency department visit for COPD	Hospitalization for COPD	Any hospital-based care for COPD‡
	Hazard ratio (95% CI)	Hazard ratio (95% CI)	Hazard ratio (95% CI)
None (n = 445)	1.0 (referent)	1.0 (referent)	1.0 (referent)
Lower level SHS exposure (n = 200)	1.40 (0.96 to 2.05) P = 0.078	1.37 (0.72 to 2.61) P = 0.34	1.52 (1.06 to 2.18) P = 0.023
Higher level SHS exposure (n = 164)	1.41 (0.94 to 2.13) P = 0.097††	1.15 (0.51 to 2.59) P = 0.73	1.40 (0.94 to 2.10) P = 0.099‡‡

Notes: Multivariable Cox proportional hazards analysis controlling for age, sex, race, educational attainment, smoking history, COPD severity score, and BODE score. Results are hazard ratio for lower level HS exposure vs none; higher level SHS exposure vs none;

* Based on validated survey instrument that assessed duration of SHS exposure (hours) during the past six days in a variety of microenvironments. Lower level and higher level were divided at the median among those with any exposure;

^† Emergency department visits and hospitalizations for COPD were ascertained from Kaiser Permanente Northern California computerized databases (see Methods);

^‡ Combined endpoint of either hospitalization or emergency department visit for COPD;

^†† p = 0.08 from Cox model using backwards selection;

^‡‡ p = 0.085 from Cox model using backwards selection.

Abbreviations: COPD, chronic obstructive pulmonary disease; SHS, secondhand smoke.