Table 1 Descriptions of covariates available from the GERA cohort study.

From: Birth weight is not causally associated with adult asthma: results from instrumental variable analyses

Covariates

Code and proportion (%)

Education

0: Other (4.97); 1: Elementary, High School or Technical School (12.6); 2: Some college (23.3); 3: College/Graduate School (59.1)

Income

1: <$39,999 (16.0); 2: $40,000–$59,999 (16.6); 3: $60,000–$99,999 (30.3); 4: >$100,000 (37.1)

BMI

1: < = 18 (1.66); 2: 19–25 (44.6); 3: 26–29 (28.7); 4: 30–39 (22.0); 5: > 40 (3.00)

Gender

1: male (39.9); 2: female (60.1)

General health

1: Excellent (19.3); 2: Very Good (38.2); 3: Good (33.7); 4: Fair/Poor (8.74)

Smoking

0: 0 pack years (57.2); 1: < = 10 pack years (14.9); 2: 10~20 pack years (15.3); 3: 20~30 pack years (8.76); 4: > 30 pack years (3.85)

Alcohol

1: no days (35.6); 2: 1 day (14.3); 3: 2–4 days (20.8); 4: 5–6 days (10.5); 5: every day (18.8)

  1. Note: GERA: Genetic Epidemiology Research on Aging; BMI: body mass index; all the covariates were incorporated into the logistic regression as continuous variables.
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