Table 1.

Characteristics of 10 Case-Control Studies Included in a Meta-Analysis of the Association Between Atopy and Leukemia, 1952–March 2009

First Author, Country, and Year (Reference No.)	Study Design	Age Range, years	Source of Cases	Source of Controls	No. of Cases	No. of Controls	Assessment of Exposure	Exposure Variables	Matching/Adjustment Factors
Fraumeni, United States, 1964 (19)a	Case-control study (National Cooperative Leukemia Study)	0–15	12 medical centers participating in National Cooperative Leukemia Study	Neighborhood controls	498	498	Parental interview	Atopic allergy (i.e., asthma, eczema, hay fever)	Matching: neighborhood, age, birth order, family size, race
			Participation rate: NA	Participation rate: NA					Adjustment: none
Bross, United States, 1972 (20)b	Case-control study (Tri-State Survey)	1–14	Cancer registries in the sample areas (New York, Maryland, Minnesota)	Multistage random sample of households in sample areas	141	357	Parental interview	Allergic diseases (i.e., asthma, hives)	Matching: NA
			Participation rate: NA	Participation rate: NA					Adjustment: age group (1–4, 5–9, or 10–14 years)
Nishi, Japan, 1989 (13)	Case-control study	0–14	All children with immunologically ascertained non-T-cell ALL at 9 hospitals in Hokkaido Prefecture, Japan	Health centers and hospitals in case residential areas, recruited at routine health examinations	63 ALL	126	Maternal interview	Atopic diathesis (i.e., history of asthma or atopic dermatitis)	Matching: age, sex, district of residence at diagnosis
			Participation rate: 100%	Participation rate: NA					Adjustment: age, sex, district of residence at diagnosis
Wen, United States, 2000 (21)	Case-control study (Children's Cancer Group)	0–14	Children's Cancer Group member institutions in the United States	RDD	1,842 ALL	1,986	Maternal telephone interview	Allergic disorders (i.e., asthma, eczema, hay fever, hives, food or drug allergies), asthma, eczema, hay fever, hives	Matching: age (within 25% of age of diagnosis, with a maximum of ±2 years), race (white, black, other), telephone area code and exchange
			Participation rate: 92%	Participation rate: 76.5%					Adjustment: age, race, telephone area code and exchange, months of breastfeeding, maternal education, maternal race, family income
Schüz, Germany, 2003 (22)	Pooled results from 3 case-control studies	0–14	Nationwide German Childhood Cancer Registry (>95% complete)	Local resident registration offices	1,130 ALL, 164 AML	2,957	Self-administered postal questionnaire completed by parents	Atopic disease (i.e., asthma, neurodermatitis, hay fever), asthma, neurodermatitis, hay fever, hives	Matching: gender, date of birth (±1 year), community
			Participation rate: 78%	Participation rate: 67%					Adjustment: age, year of birth, gender, degree of urbanization (rural, urban, mixed), SES (average, high)
Spector, United States, 2004 (12)	Case-control study	0–6	Databases of 4 HMOs in western United States	Databases of 4 HMOs in western United States	180 ALL	718	Subjects’ medical records (diagnosis by a physician)	Allergic conditions (i.e., asthma; eczema; atopy or hives; food, drug, or bee allergy; pollen, dust, or dander allergy), asthma, eczema	Matching: HMO, gender, date of birth (±2 weeks)
			Participation rate: 100%	Participation rate: 100%					Adjustment: age, gender, race, HMO. Results mutually adjusted for individual allergic conditions.
Jourdan-Da Silva, France, 2004 (11)	Population-based case-control study	0–14	National Registry of Childhood Leukemia and Lymphoma in France (all cases aged <15 years)	Randomly selected from general population via RDD on the basis of expected distribution of cases	408 ALL, 65 AML	567	Self-administered questionnaire completed by mothers	Asthma	Matching: age, gender, region of residence at diagnosis
			Participation rate: 73%	Participation rate: 71%					Adjustment: gender, age, region
Rosenbaum, United States, 2005 (23)	Case-control study (31 counties of New York State)	0–14	Institutional tumor registries and departmental records at 4 major medical centers	Randomly selected via Live Birth Certificate Registry (New York State Department of Health)	255 ALL	760	Self-administered postal questionnaire completed by parents	Allergy history (i.e., asthma; eczema; food, drug, or bee allergy; pollen, dust, or cat/dog dander allergy), asthma, eczema	Matching: sex, race (white/nonwhite), birth year
			Participation rate: 71%	Participation rate: 55%					Adjustment: maternal smoking (yes/no), maternal education (years), breastfed (yes/no), race, birth year
Söderberg, Sweden, 2006 (14)c	Population-based case-control study	0–18	All cases in Swedish Cancer Registry	Randomly selected from Swedish nationwide population registry	875 ALL, 132 AML	14,865	Swedish Hospital Discharge Registry	Asthma	Matching: sex, 5-year age group, year of diagnosis
			Participation rate: 100%	Participation rate: 100%					Adjustment: sex, age, SES
Hughes, United Kingdom, 2007 (10)	Population-based case-control study (United Kingdom Childhood Cancer Study)	0–14	United Kingdom residents diagnosed with malignancy	Randomly selected from primary care population registers	839 (720 ALL, 101 AML)	1,337	Primary care records	Allergies (i.e., asthma, eczema, hay fever), asthma, eczema, hay fever	Matching: age, sex, region of residence at diagnosis
			Participation rate: 92%	Participation rate: 70%					Adjustment: age (single years), sex, region of residence, deprivation index

Abbreviations: ALL, acute lymphoblastic leukemia; AML, acute myeloid leukemia; HMO, health maintenance organization; NA, not available; RDD, random digit dialing; SES, socioeconomic status.

^aCrude odds ratio was calculated from the data provided.

^bAge-adjusted odds ratio was calculated from data provided in the published article (55).

^cResults for subjects under age 19 years were obtained from the first author via personal communication.