Application of three-level linear mixed-effects model incorporating gene-age interactions for association analysis of longitudinal family data.

Longitudinal studies that collect repeated measurements on the same subjects over time have long been considered as being more powerful and providing much better information on individual changes than cross-sectional data. We propose a three-level linear mixed-effects model for testing genetic main effects and gene-age interactions with longitudinal family data. The simulated Genetic Analysis Workshop 16 Problem 3 data sets were used to evaluate the method. Genome-wide association analyses were conducted based on cross-sectional data, i.e., each of the three single-visit data sets separately, and also on the longitudinal data, i.e., using data from all three visits simultaneously. Results from the analysis of coronary artery calcification phenotype showed that the longitudinal association tests were much more powerful than those based on single-visit data only. Gene-age interactions were evaluated under the same framework for detecting genetic effects that are modulated by age.

Left atrial systolic force and cardiac markers of preclinical disease in hypertensive patients: the Hypertension Genetic Epidemiology Network (HyperGEN) Study.

BACKGROUND: Left atrial systolic force (LASF) has been recently reported to be associated with prolonged left ventricular (LV) relaxation and concentric LV geometry in a clinical setting. This study analyzes the association of increased LASF to LV geometry and function in hypertensive patients from a population study. METHODS: Doppler echocardiographic findings were examined in 684 subjects with treated hypertension and without prevalent cardiovascular disease from the Hypertension Genetic Epidemiology Network (HyperGEN) Study (426 African American, 448 female, 125 diabetic, 174 obese; age 53.8+/-10.8 years). The LASF was assessed from the mitral orifice area and pulse-wave Doppler peak A flow velocity. The LASF was defined as being high if >14.33 kdynes (90th percentile of the normal distribution in 246 normal adults). RESULTS: The LASF was high in 269 participants (39.3% of study population), who were older and had higher mean body mass index (all P<.01). Participants with high LASF had higher systolic BP and heart rate (both P<.01) but similar diastolic BP. After controlling for covariates, participants with high LASF exhibited higher LV dimensions and mass than those with normal LASF (all P<.01). The prevalence of LV hypertrophy was also higher (P<.001). Participants with high LASF exhibited normal ejection fraction, higher stroke volume, cardiac output, E and A velocities, slower E deceleration, and lower E/A ratio than those with normal LASF (all P<.01). CONCLUSIONS: Enhanced LASF is associated with LV hypertrophy, normal LV chamber function, increased cardiac output, and prolonged relaxation. The LASF is a preload-dependent measure.