However, the use of different prediction equations lead to variable numbers of subjects in the respective categories, resulting in different estimates of FEV1 decline, variances and levels of statistical significance.
The decline in variance in relative fitness was mostly explained by the decrease in variance in relative child survival (up to 1974, 5.20 × 10−2; 1975 onward, 8.15 × 10−3; ρ = −0.84; p < 0.001; Figure 1B), itself the result of the decrease in mean child mortality.
Although reductions in prereproductive mortality drove the decline in variance in relative total fitness, we observed an increase in the variance of relative fertility (up to 1974, 5.57; 1975 onward, 6.32; ρ = +0.49; p < 0.001; Figure 1C), a pattern that also marks the first stages of other demographic transitions [ 2, 10, 13].
The highest decline in variance over the next 5 years occurred in the expected number of years lived adjusted only for dispersion (e C ).
For example, Galton's "regression to the mean" is defined as a decline in variance over generations (p. 102), which is misleading for modern readers.
Therefore, this suggests a decline in variance in age-at-death or the process of compression of mortality over the time period (36, 46, 49).
We performed a mutation accumulation (MA) experiment in Tetrahymena thermophila, a species that can reproduce sexually and asexually in nature, and measured both the mean decline and variance increase in fitness of 20 lines.
However, the declines in variances become much slower thereafter, reflecting the slow decay of linkage disequilibrium and the gradual increase in the number of new segregating variants following a population expansion.
First, as fertility and mortality decline, the total variance in relative fitness [ 9 14] and thus the "opportunity" for selection both change [ 9, 15].
The ADNI longitudinal data demonstrate acceptable decline rate and variance for the ADAS-cog and CDR-SB in amnestic MCI; the size of trials adequately powered to demonstrate slowing of cognitive/clinical progression would be large but perhaps manageable.
