Characteristics of the included studies
| Reference, year | Country | Study design | Sample size* | Percentage of women | Age (range/mean±SD) | Information on diseases/symptoms | Socioeconomic indicator | Respiratory function indices† | Relationship between respiratory function and socioeconomic indicators |
| Ware et al, 198438 | USA | Longitudinal | 7145 | n.m. | 6–9 | Respiratory symptoms | SES Index, parental education and occupation | FEV1, FVC (Dockery et al, 1983 equations) | No association |
| Goren and Goldsmith, 198629 | Israel | Cross-sectional | n.m. | n.m. | Second and fifth grade | Respiratory symptoms | Crowding Index, parental education | FVC, FEV1, FEV1/FVC, PEF | Positive association—higher crowding index and lower maternal education was associated with reduced respiratory function measured by FEV1/FVC |
| Kauffmann et al, 198952 | France | Cross-sectional | 1160 (828) | 48 | 6–10 | n.m. | Maternal education | FEV1,FVC, FEF25–75 | No association |
| Azizi and Henry, 199055 | Malaysia | Cross-sectional | 1214 | 42.1 | 7–12 | Respiratory symptoms | Paternal education | FEV1,FVC, FEF25–75 | No association |
| Kitchen et al, 199253 | Australia | Longitudinal | 223 | ≈50 | 8 | Asthma and respiratory symptoms | Social class (parental occupation), maternal education | VC, FVC, FEV1 | Positive association—lower social class was associated with reduced respiratory function measured by FVC and FEV1/FVC |
| Demissie et al, 199633 | Canada | Cross-sectional | 989 (916) | n.m. | 5–13 | n.m. | SES Score (parental income, education, occupation) | FEV1, FVC, FEV1/FVC | Positive association—low SES was associated with reduced respiratory function measured by FEV1 and FVC, in boys |
| Lercher and Schmitzberger, 199754 | Austria | Cross-sectional | 644 | n.m. | 7.5–11 | n.m. | Maternal education | FVC, FEV1, PEF, MEF25, MEF50, MEF75 | Positive association—low maternal education was associated with reduced respiratory function measured by FEV1 |
| Hancox et al, 200447 | New Zealand | Longitudinal | 1037 (980) | 48 | 0–26 | Asthma and respiratory symptoms | SES (parental occupation, education, income), parental income | FEV1/FVC | No association |
| Harik-Khan et al, 200434 | USA | Cross-sectional | 752 | 50.9 | 8–12 | Healthy | Family head education, Poverty Index | FEV1, FVC (Hankinson et al, 1999 equations) | Positive association—poverty in boys and lower parental education in girls was associated with reduced respiratory function measured by FEV1, FVC |
| Raju et al, 200535 | India | Cross-sectional | 2616 | 40 | 5–15 | Healthy | SES with Modified Kuppuswamy Scale (parental education and occupation, family income) | FEV1, FVC, FEV1/FVC, PEFR | Positive association—lower SES was associated with reduced respiratory function measured by all indices |
| Balmer et al, 200831 | USA | Longitudinal | 77 | 55 | 6–8.9 | Cystic fibrosis | Advantage Index (household income, parental education,l social capital) | FEV1
(Wang et al, 1993 equations) | Positive association—lower scores in the advantage index was associated with reduced respiratory function measured by FEV1 |
| Bennett et al, 200839 | USA | Cross-sectional | 87 | 56.3 | 7–18 | Cystic fibrosis | SES (parental education, occupation) | FEV1 | Positive association—lower SES was associated with reduced respiratory function measured by FEV1 |
| Suglia et al, 20089 | USA | Cross-sectional | 313 | 50 | 6–7 | Respiratory symptoms | Maternal education | FVC, FEV1, FEF25–75 | No association |
| Trabelsi et al, 200830 | Tunisia | Cross-sectional | 756 | 48.7 | 6–16 | Healthy | SES (parental occupation) | FVC, FEV1, FEV1/FVC, PEF, MEF50, MMEF25–75 | Positive association—lower SES was associated with reduced respiratory function measured by all indices |
| Tennant et al, 20107 | UK | Longitudinal | 252 | 47.2 | 14 | Respiratory symptoms | Social class (paternal occupation), housing conditions | FEV1
(Pistelli et al, 2000 equations) | Positive association—lower social class was associated with reduced respiratory function measured by FEV1 |
| Yogev-Baggio et al, 201056 | Israel | Longitudinal | 1181 | ≈55 | 9.3±1.6 | Healthy and respiratory symptoms | Paternal education, housing density | Changes in FVC and FEV1 | Positive association—lower fathers' education was associated with reduced respiratory function measured by FEV1 in healthy children |
| Menezes et al, 20116 | Brazil | Longitudinal | 4005 | 51 | 14–15 | Asthma and respiratory symptoms | Family income | FEV1, FVC | Positive association—lower family income was associated with reduced respiratory function measured by FEV1 and FVC, in girls |
| Slachtova et al, 201132 | Multiple‡ | Cross-sectional | 24 010 | 48.9 | 6–12 | n.m. | Parental education | FEV1, FVC, PEF, MMEF | No association |
| Wu et al, 201210 | Taiwan | Cross-sectional | 3994 | 49.3 | 12.4±0.6 | n.m. | Area-level SES (occupation, income, education) | FEV1, FVC, FEF25–75, PEF | Negative association—higher SES was associated with reduced respiratory function measured by FEV1, FVC, FEF25–75 |
| Taylor-Robinson et al, 201343 | UK | Longitudinal | 8055 (5324) | 47 | <18 | Cystic fibrosis | Index of multiple deprivation based on area of residence | FEV1% predicted | Positive association—reduced respiratory function measured by FEV1 was found in the most deprived quintile when compared with the least deprived quintile |
| Rebacz-Maron and Parafiniuk, 201448 | Tanzania | Cross-sectional | 255 | n.m. | 12.8–24.0 | n.m. | Family material situation, parental education | FEV1, FVC | Positive association—lower family material situation was associated with reduced respiratory function measured by FEV1 and FVC (<17.5 years) |
| Siniarska et al, 201449 | Poland | Cross-sectional | 444 | 50.7 | 13–16 | n.m. | SES (parental education, number of rooms, sibling size) | VC, FEV1, TV, MV, IRV, ERV, AP, RR | No association |
| Cogen et al, 201540 | USA | Longitudinal | 946 | 49.7 | 6–12 | Cystic fibrosis | Maternal education, household income | FEV1 (Wang et al 1993 and Hankinson et al 1999 equations) | No association |
| Galobardes et al, 201544 | UK | Longitudinal | 6378 | 49.8 | 7–8 | Asthma and respiratory symptoms | Parental education and occupation, household income, housing tenure | FEV1, FVC, FEF25–75 | Positive association—low paternal education was associated with reduced respiratory function measured by FEV1 |
| Lum et al, 20158 | UK | Longitudinal | 2171 (1901) | ≈50 | 5.2–11.8 | Asthma and respiratory symptoms | Receiving free school meals, family affluence scale, index of multiple deprivation; | FEV1, FVC (equations for multiethnic schoolchildren, 2012) | No association |
| Martínez-Briseño et al, 201550 | Mexico | Longitudinal | 2641 (1671) | n.m. | 8–17 | Healthy | Monthly family income, parental education | FEV1, FVC, FEV1/FVC (Martínez-Briseño et al 2013 equations) | Positive association—lower income and education was associated with reduced respiratory function measured by all indices |
| Sanders et al, 201541 | USA | Longitudinal | 484 | ≈50 | 6–7 | Cystic fibrosis | Maternal education, household income | FEV1
(Wang et al 1993 equations) | Positive association—low maternal education was associated with reduced respiratory function measured by FEV1 |
| Cakmak et al, 201651 | Canada | Cross-sectional | 2328 (1528) | ≈50 | 9–11 | Asthma and respiratory symptoms | Parental education, family income | FEV1, FVC | Positive association—lower education and income was associated with reduced respiratory function measured by FEV1, FVC |
| Lum et al, 201645 | UK, India | Cross-sectional | 8124 (2549) | 43.7 | 5–17 | n.m. | Socioeconomic circumstances | FEV1, FVC (GLI equations, 2012) | Positive association—lower SEC was associated with reduced lung function measured by respiratory function z-scores in Hyderabad |
| Kuti et al, 201736 | Nigeria | Cross-sectional | 250 | 50.8 | 9–17 | n.m. | Overcrowding, socioeconomic class (parental occupation and education) | FEV1, FVC, FEV1/FVC (Knudson et al 1983 equations) | Positive association—lower social class was associated with reduced lung function measured with FEV1 and FVC in male participants from urban areas |
| Nowakowski et al, 201737 | Poland | Cross-sectional | 152 | 100 | 19–24 | n.m. | SES Index (size of dwelling place, number of siblings, parental education | FEV1, FVC, FEV1/FVC | Positive association—lower father’s education and SES was associated with reduced respiratory function measured by FEV1/FVC |
| Ong et al, 201742 | USA | Longitudinal | 1375 (1050) | 50 | 6–13 | Cystic fibrosis | Maternal education, household income | FEV1
(Wang et al 1993 and Hankinson et al1999 equations) | Positive association—lower education and income was associated with reduced respiratory function measured by FEV1 |
| Saad et al, 201746 | UK | Cross-sectional | 90 | 52.2 | 18–23 | Asthma and respiratory symptoms | Socioeconomic status (parental and grand parental education and occupation) | FEV1, FVC, FEV1/FVC (NHANES III reference equations) | Positive association—higher maternal education and higher paternal occupation were associated with higher respiratory function measured by FVC. |
*Total sample size (and the number of participants included in the analysis of lung function indices by SES indicator).
†When respiratory function indices were computed using reference equations, it is mentioned in brackets.
‡Multiple countries: Poland, Hungary, Slovakia, The Czech Republic, Netherlands, Germany, Austria, USA.
AP, apnoea; ERV, expiratory reserve volume; FEF, forced expiratory flow; FEV1, forced expiratory volume during first second; FEV1/FVC, ratio between FEV1 and FVC; FVC, forced vital capacity; GLI, Global Lung Function Initiative; IRV, inspiratory reserve volume; MEF, maximal expiratory flow; MMEF, maximum mid-expiratory flow; MV, minute ventilation; n.m., not mentioned; NHANES, National Health and Nutrition Examination Survey; PEF, peak expiratory flow; PEFR, peak expiratory flow rate; RR, respiration rate per minute; SEC, socioeconomic circumstances; SES, socioeconomic status; TV, tidal volume; VC, vital capacity.