BMC Public Health 2004, 4 http://www.biomedcentral.com/1471-2458/4/16 ▪ South: Delaware, Maryland, District of Columbia, Vir- ginia, West Virginia, Kentucky, Tennessee, North Caro- lina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, Oklahoma, Arkansas, and Texas. ▪ West: Washington, Oregon, California, Nevada, New Mexico, Arizona, Idaho, Utah, Colorado, Montana, Wyo- ming, Alaska, and Hawaii. Individuals Individuals with eligible birth defects were identified using the NHIS Core Condition files. Once identified, unique household and person identifiers were created by concatenating the first seven and eight fields, respectively. These identifiers were used to ascertain individuals and families with greater than one birth defect as well as to link other NHIS datasets to obtain personal and house- hold characteristics for comparison. Households Four groups of households were extracted from the NHIS: 1) single non-familial, which includes a proband with an isolated birth defect and no other family member living in the same household with a birth defect; 2) single familial, which includes a proband and at least one more family member living in the same household, all with an isolated birth defect; 3) multiple non-familial, which includes a proband with more than one birth defect and no other family member living in the same household with a birth defect, and 4) multiple familial, which includes a proband and at least one more family member living in the same household, all with two or more birth defects. The conditions reported by the individuals living in these households are presented in Table 1. Individual and household characteristics were obtained from the 1994/ 1995 NHIS survey and summarized in Table 2. Table 2: Individual and household characteristics of the four groups with birth defects extracted from the NHIS (1994/1995) Single Non-Familial n (% of total) Multiple Non-familial n (% of total) Single Familial n (% of total) Multiple Familial n (% of total) Individual Characteristics Total Number of Individuals Mean age Males Ethnicity Caucasian African-American Other Household Characteristics Total Number of Households Mean Family Size Income <$10,000 $10,000 to <$20,000 $20,000 to <$30,000 $30,000 to <$40,000 $40,000 to <$50,000 $50,000 + Below NHIS poverty threshold* Highest Education of Responsible Adult Family Member 1 – 8 years (elementary) 9 – 11 years (high school) 12 years (high school graduate) 1 – 3 years (college) 4 years (college graduate) 5 + (post-college) Region of Residence Northeast Midwest South West 1,083 33.7 489 (45.2) 907 (83.8) 117 (10.8) 48 (4.4) 1,083 3.5 77 (7.1) 194 (18.0) 169 (15.7) 129 (12.0) 113 (10.5) 262 (24.3) 140 (12.9) 34 (3.1) 89 (8.2) 351 (32.4) 281 (26.0) 177 (16.3) 148 (13.7) 212 (19.6) 218 (20.1) 388 (35.8) 265 (24.5) 55 28.3 27 (49.1) 46 (83.6) 2 (3.6) 7 (12.7) 55 3.5 3 (5.5) 10 (18.2) 9 (16.4) 6 (10.9) 5 (9.1) 15 (27.3) 7 (12.7) 1 (1.8) 1 (1.8) 17 (30.9) 16 (29.1) 7 (12.7) 12 (21.8) 9 (16.4) 18 (32.7) 15 (27.3) 13 (23.6) 113 26.0 51 (45.1) 90 (79.7) 6 (5.3) 17 (15.0) 54 4.35 6 (11.1) 8 (14.8) 9 (16.7) 12 (22.2) 4 (7.4) 13 (24.1) 9 (16.7) 2 (3.7) 6 (11.1) 19 (35.2) 12 (22.2) 9 (16.7) 6 (11.1) 10 (18.5) 15 (27.8) 14 (25.9) 15 (27.8) 16 29.8 5 (31.3) 12 (75.0) 4 (25.0) 0 8 4.0 2 (25.0) 1 (12.5) 2 (25.0) 2 (25.0) 0 1 (12.5) 2 (25.0) 1 (12.5) 2 (25.0) 3 (37.5) 0 0 2 (25.0) 3 (37.5) 3 (37.5) 2 (25.0) 0 *NHIS poverty levels for 1994 and 1995 are based on family size, number of children below 18 years of age, and family income using the 1993 and 1994 poverty levels derived from the August 1994 and 1995 Current Population Surveys. Page 3 of 7 (page number not for citation purposes)