Occurrence of conotruncal heart birth defects in Texas: a comparison of urban/rural classifications

(1) Determine if there is an association between 3 conotruncal heart birth defects and urban/rural residence of mother. (2) Compare results using different methods of measuring urban/rural status.

Data were taken from the Texas Birth Defects Registry, 1999-2003. Poisson regression was used to compare crude and adjusted birth prevalence.

Based on residences of births in Texas, the values for urban influence code (UIC), rural urban continuum code (RUCC), and rural urban commuting area (RUCA) were highly correlated with each other and, less highly, to percentage of land in crops. For tetralogy of Fallot, the most rural category consistently showed the highest prevalence ratio for all measures. The adjusted prevalence ratio for highest percentage cropland was 1.73 [95% CI, 1.14-2.51] using natural breaks and 1.42 [95% CI, 1.07-1.86] using quartiles. The trend with cropland percentage was significant (P < .03), whether crude or adjusted. The crude trend was also significant using RUCC. Neither truncus arteriosus nor transposition of the great arteries exhibited consistent associations with urban or rural residence.

The urban/rural measures were generally correlated with each other; as a broad measure, RUCA has advantages for many health studies. Tetralogy of Fallot was most prevalent in rural areas; that pattern was strongest using percentage of land in crops.