Recent observational studies of type Ia supernovae (SNeIa) suggest correlations between the brightness of an event and properties of the host galaxy that appear to involve the age of the progenitor population. One way to influence the explosion systematically is through the central density at ignition, which is determined by the mass of the white dwarf before the onset of accretion, the white dwarf cooling time (prior to the onset of accretion), the subsequent accretion history, and neutrino losses. The dependence of the central density on cooling time connects the central density to the age of the progenitor and therefore the average stellar age of the host galaxy. We find that with increased progenitor central density, production of Fe-group material does not change but production of 56Ni decreases, which we attribute to a higher rate of neutronization occurring at higher density. These results offer an explanation for the observation of dimmer SNeIa in galaxies with an older stellar population. We also demonstrate a strong dependence of the 56Ni yield in our results on the morphological structure of the burning front during the early deflagration, suggesting that a statistical ensemble of simulations is necessary when studying the systematics of SNeIa.