Baseline characteristics of the study participants by treatment group*
| Intervention (n=103) | Usual care (n=102) | |
| Socioeconomic status | ||
| Multiple Deprivation Index rank† | 6569.7 (5432.5) | 6643.1 (5679.0) |
| Housing tenure | ||
| Own/mortgaged | 6 (6%) | 9 (9%) |
| Private rent | 48 (47%) | 37 (36%) |
| Council/local authority | 47 (46%) | 53 (52%) |
| Other | 2 (2%) | 3 (3%) |
| Adults, n | 1.5 (0.6) | 1.6 (0.7) |
| Children, n | 2.1 (1.2) | 2.2 (1.2) |
| Age of children, years | 3.6 (2.6) | 3.3 (2.3) |
| Cigarettes smoked daily inside the home, n | ||
| Mean (SD) | 15.0 (11.0) | 15.0 (11.0) |
| Median (IQR) | 12.0 (8.0–20.0) | 12.0 (7.0–20.0) |
| Caregiver Heaviness of Smoking Index‡ | 2.6 (1.5) | 2.5 (1.6) |
| Seasonality at baseline appointment | ||
| Warm | 56 (54%) | 53 (52%) |
| Cold | 47 (46%) | 49 (48%) |
| Ethnicity | ||
| Other | 8 (8%) | 4 (4%) |
| White British | 95 (92%) | 98 (96%) |
| Partner cohabits all of the time | ||
| Other | 60 (58%) | 58 (57%) |
| Yes | 43 (42%) | 44 (43%) |
| Age of caregiver, years | 28.1 (6.2) | 27.9 (6.6) |
| Air quality at home (PM2.5), µm/m3§ | ||
| Mean (SD) | 54.6 (71.1) | 46.5 (52.8) |
| Median (IQR) | 33.4 (12.3–77.8) | 30.5 (14.1–72.7) |
| Maximum PM2.5 | 437.5 (590.6) | 401.7 (433.6) |
| Cotinine index child, ng/mL | ||
| Mean (SD) | 7.5 (8.1) | 7.6 (8.0) |
| Median (IQR) | 4.76 (6.21) | 4.77 (7.48) |
*Means and SD for most variables, unless otherwise stated. There was no statistically significant difference between groups in any of the variables listed.
†The Index of Multiple Deprivation rank goes from 1 (most deprived area) to 32 844 (least deprived area).
‡Heaviness of Smoking Index derives from Fagerström Test for Nicotine Dependence but uses only two questions (how soon after waking up do you smoke your first cigarette and how many cigarettes a day do you smoke). Scores range from 1 to 6, where higher scores are for higher dependency and lower scores are for lower dependency.
§Indoor air pollution concentration, 24 hours average PM2.5 (21), and in our case, 16–24 hours average PM2.5 is measured in µm/m3, which refers to milligrams of pollutant per cubic metre of air (in this case the pollutant is PM2.5).