Further , independent of confounders , office-day BP showed significant intrafamilial aggregation and heritability ( SBP : h = 0.510.10 , P < 0.0001 ; DBP : h = 0.370.09 , P < 0.0001 ) , effects that persisted with further adjustments for office , day , or day-night BP ( P < 0.0005 for SBP and DBP ) .