Table 1.
Characteristics of seven included studies in the meta-analysis.
| Study | Baseline Study Dates | Country | Study Design | Follow-Up Time | Participants | Number of Events | Residential Distance to Major Roadways | Definitions of Major Roadways or High Traffic Intensity | Adjustment Factors | Quality * |
|---|---|---|---|---|---|---|---|---|---|---|
| Dzhambov, 2016 [13] | 2014 | Bulgaria | Cross-sectional | NA | 513 | 35 | Home located near to roads with high traffic intensity | Extreme traffic intensity reported by participants. | Sex, age, socioeconomic classes, occupations, dietary habits, alcohol consumption, PM2.5, loud noise, and smoking. | B |
| Heidemann, 2014 [19] | 1997–1998 | Germany | Cohort | 12.1 years | 3604 | 252 | Home located near to roads with high traffic intensity | Extremely busy traffic reported by participants. | Sex, age, smoking, heating of house, educational status, BMI, waist circumference, sport activity, and parental history of diabetes. | A |
| Andersen, 2012 [12] | 1993–1997 | Denmark | Cohort | 9.7 years | 51,818 | 2877 | <50 m from major roadways | A road with at least 10,000 vehicles/day which was determined by the residential address and the public traffic data. | Adjusted for sex, hypertension, hypercholesterolemia, myocardial infarction, BMI, waist-to-hip ratio, smoking status, smoking duration, smoking intensity, environmental tobacco smoke, educational level, physical/sports activity in leisure time, alcohol consumption, fruit consumption, fat consumption, and calendar year. | A |
| Hoffmann, 2011 | 2000–2003 | Germany | Cohort | 5 years | 3398 | 309 | <100 m from major roadways | A road with busy traffic but how it was defined in details was unclear. | Adjusted for sex, age, body mass index, education, smoking, physical activity, and city of residence. | B |
| Dijkema, 2011 [10] | 1998–2000 | Netherlands | Cross-sectional | NA | 8018 | 213 | <100 m from major roadways | A road with at least 5000 vehicles/day which was determined by the residential address and the traffic data from Geographical Information System. | Adjusted for average monthly income, age (continuous) and gender. | B |
| Puett, 2011 NHS [11] | 1989 | USA | Cohort | 13 years | 74,412 | 3784 | <100 m from major roadways | Major roadways, such as interstates highways and major noninterstate roads which was determined by the residential addresses and the public traffic data. | Adjusted for age, season, calendar year, state of residence, time-varying cigarette smoking (status and pack-years), time-varying hypertension, baseline BMI, time-varying alcohol intake, baseline physical activity, and time-varying diet. | A |
| Puett, 2011 HPHS [11] | 1989 | USA | Cohort | 13 years | 15,048 | 688 | <100 m from major roadways | Major roadways, such as interstates highways and major noninterstate roads which was determined by the residential addresses and the public traffic data. | Adjusted for age, season, calendar year, state of residence, time-varying cigarette smoking (status and pack-years), time-varying hypertension, baseline BMI, time-varying alcohol intake, baseline physical activity, and time-varying diet. | A |
| Kramer, 2010 [18] | 1985–1994 | Germany | Cohort | 16 years | 1775 | 187 | <100 m from major roadways | A road with more than 10,000 cars/day which was determined by the residential addresses and data on road traffic from environmental agency. | Adjusted for age, BMI, heating with fossil fuels, workplace exposure with dust/fumes, extreme temperatures, smoking, and education. | A |
* Quality was assigned as A quality with 7–9 stars, B quality with 4–6 stars, and C quality with 0–3 stars; USA = United States of America; BMI, body mass index; NHS, Nurses’ Health Study; HPFS, Health Professionals Follow-Up Study; NA, not available.