Environmental tobacco smoke exposure and heart disease: A systematic review

Table 2 Potential confounding variables adjusted for and definition of never smoker

Study No.	Ref.1	Variables adjusted for2	Definition of never smokers3
1	Hirayama[29]	Sex, age, marital status	Never cigarettes
2	Garland et al[30]	Sex, age, marital status, blood pressure, cholesterol, obesity	Never cigarettes
3	Lee et al[31]	Sex, age, marital status	Never NOS
4	Martin et al[32]	Sex, marital status, blood pressure, obesity, alcohol, diabetes, family history of heart disease, exercise	Never NOS
5	Svendsen et al[33]	Sex, age, marital status, blood pressure, cholesterol, social class, obesity, alcohol	Never any product
6	Butler[34]	Sex, age, marital status	Never cigarettes
7	Palmer et al[35]	Sex, marital status	Never NOS
8	Hole et al[36]	Sex, age, blood pressure, cholesterol, social class, obesity	Never NOS
9	Jackson[37]	Sex, age, social class, obesity, family history of heart disease	Never NOS
10	Sandler et al[38]	Sex, age, social class, personal history of heart disease	Never any product
11	Humble et al[39]	Sex, age, marital status, blood pressure, cholesterol, obesity	Never NOS
12	Dobson et al[40]	Sex, age, social class, obesity, personal history of heart disease	Never cigarettes
13	Gardiner et al[41]	Sex, age, hospital admission date	Never any product
14	La Vecchia et al[42]	Sex, age, marital status, blood pressure, cholesterol, social class, obesity, diabetes, family history of heart disease, coffee	Never NOS
15	Layard[25]	Sex, age, marital status, race	Never 100 cigarettes in lifetime
16	Le Vois et al[26] (CPS I)	Sex, age, marital status, race	Never NOS
17	Mannino et al[43]	Sex, age, social class, race, housing	Never NOS
18	Muscat et al[44]	Sex, age, blood pressure, social class, race	Never one cigarette, pipe or cigar per day for more than a year
19	Tunstall-Pedoe et al[45]	Age, blood pressure, cholesterol, housing	Never any product and cotinine < 17.5 mg/mL
20	Steenland et al[46]	Sex, age, marital status, blood pressure, social class, obesity, alcohol, diabetes, exercise, personal history of heart disease, occupation, oestrogen use, aspirin use, diuretic use and personal history of arthritis	Never any product daily for as long as a year (men), never cigarettes (women)
21	Janghorbani et al[47]	Sex, age, marital status	Never any product
22	Kawachi et al[48]	Sex, age, blood pressure, cholesterol, obesity, alcohol, diabetes, family history of heart disease, exercise, occupation, oestrogen use, oral contraceptive use, saturated fat intake, vitamin E intake, menopausal status and use of postmenopausal hormones	Never NOS
23	Ciruzzi et al[49]	Sex, age, blood pressure, cholesterol, social class, obesity, diabetes, family history of heart disease, exercise	Never NOS
24	McElduff et al[50]	Sex, age, social class, obesity, family history of heart disease	Never cigarettes or quit at least 10 yr ago, and not current other products
25	Spencer et al[51]	Sex, age	Never NOS
26	He et al[52]	Sex, age, blood pressure, cholesterol, family history of heart disease, personality type	Never NOS
27	Iribarren et al[53]	Sex, age, marital status, cholesterol, social class, obesity, alcohol, diabetes, race, exercise, personality type	Never any product
28	Rosenlund et al[54]	Sex, age, blood pressure, cholesterol, social class, obesity, diabetes, occupation	Never any product regularly for at least a year
29	Pitsavos et al[55]	Sex, age, blood pressure, cholesterol, obesity, alcohol, diabetes, exercise and family history of heart disease	Never cigarettes
30	Enstrom et al[27]	Sex, age, marital status, social class, obesity, race, exercise, housing, fruit or fruit juice intake and health status	Never any product4
31	Chen et al[56]	Sex, age, blood pressure, cholesterol, social class, obesity, alcohol, family history of heart disease, employment status, dietary vitamin C and fibre	Never NOS and cotinine < 17.5 mg/mL
32	Nishtar et al[57]	Sex, age, matched pair (conditional logistic regression was used)	Never NOS
33	Whincup et al[58]	Sex, age, blood pressure, cholesterol, social class, obesity, alcohol, diabetes, exercise, personal history of heart disease, town of residence, FEV1, height, triglycerides and white cell count	Never any product and cotinine < 14.1 mg/mL
34	McGhee et al[59]	Sex, age, marital status, social class	Never NOS
35	Qureshi et al[60]	Sex, age, marital status, blood pressure, cholesterol, obesity, alcohol, diabetes, race	Never NOS
36	Hedblad et al[61]	Sex, blood pressure, cholesterol, obesity, alcohol, diabetes, exercise, personal history of heart disease, triglycerides and FEV1	Never one cigarette per day
37	Stranges et al[62]	Sex, blood pressure, cholesterol, social class, obesity, alcohol, diabetes, race, exercise	Never 100 cigarettes in lifetime
38	Teo et al[63]	Sex, age, alcohol, exercise, region, consumption of fruits and vegetables	Never any product regularly
39	Wen et al[64]	Sex, age, social class, obesity, exercise, occupation, intake of meats, vegetables and fruit	Never NOS
40	Eisner et al[65]	Sex, age, marital status, social class	Never cigarettes or quit at least 20 yr ago, and < 10 pack-years
41, 42	Hill et al[66]	Sex, age, marital status, social class, race, occupation	Never NOS
43	He et al[67]	Sex, age, marital status, blood pressure, cholesterol, social class, obesity, alcohol, diabetes, family history of heart disease, exercise, triglycerides, family history of stroke	Never 100 cigarettes in lifetime
44	Sulo et al[68]	Sex, age, blood pressure, social class, obesity, diabetes, family history of heart disease, race, exercise, occupation, financial loss in pyramid schemes, emigration of spouse and/or offspring, religious observance	Never cigarettes
45	Vozoris et al[69]	Sex, age, social class, province, immigration status, presence of children younger than 12 yr in household	Never cigarettes
46	Ding et al[70]	Sex, age, blood pressure, cholesterol, social class, alcohol, diabetes, family history of heart disease, exercise, oestrogen use, history of stroke, history of gout	Never NOS
47	Gallo et al[71]	Sex, age, social class, obesity, exercise, study centre	Never NOS
48	Hamer et al[72]	Sex, age, blood pressure, cholesterol, social class, exercise, personality type, survey location, log C-reactive protein, fibrinogen	Never NOS
49	Jefferis et al[73]	Sex, age, blood pressure, cholesterol, social class, obesity, alcohol, diabetes, exercise, region, triglycerides, FEV1, C-reactive protein, interleukin 6, white cell count	Never any product or quit at least 5 yr ago, and cotinine < 15 mg/mL
50	Peinemann et al[74]	None	Never NOS
51	Chen[75]	None	Never cigarettes
52	He et al[76]	Sex, age, marital status, blood pressure, cholesterol, social class, obesity, alcohol, occupation, triglycerides	Never 100 cigarettes in lifetime
53	Clark et al[77]	Sex, age, social class, obesity, dialect, dietary fibre intake	Never NOS
54	Iversen et al[78]	Sex, age, blood pressure, cholesterol, obesity, exercise, living with a smoker (for analysis of hours spent in smoke-filled rooms), hours spent in smoke-filled rooms (for analysis of living with a smoker)	Never cigarettes
55	Kastorini et al[79]	Sex, age, blood pressure, cholesterol, obesity, diabetes, family history of heart disease, exercise, personality type, Mediterranean Diet Score	Never one cigarette a day
56	Rostron[80]	Sex, age, race, social class, alcohol, blood pressure, obesity, personal history of heart disease	Never 100 cigarettes in lifetime
57	Batty et al[81]	Sex, age, social class, alcohol, diabetes, exercise, personal history of heart disease, personal history of cancer	Never NOS
58	Shiue[82]	Sex, age, race, social class, alcohol, survey weighting, exercise, blood pressure, obesity	Never any product

¹First author of paper;

²In some cases similar adjustment variables have been considered under one name. Thus blood pressure includes hypertension; social class includes education and income; obesity includes weight; family history of heart disease includes family history of hypertension; and housing includes urban-rural;

³Never any product: Never smoked cigarettes, pipes or cigars; Never NOS: Never smoked, product unspecified;

⁴Questions on pipe and cigar smoking were asked at baseline, but not at the follow-up interviews.