All of this is "normal aging". Dementia is "normal aging." Normal aging is terrible and creates a varying distribution of disease states in people. Those disease states are the end of a random walk of primary aging (i.e. unavoidable molecular damage caused by the normal operation of metabolism) and secondary aging (i.e. being fat, smoking, etc, things that add extra molecular damage or extra consequences that are similar to the consequences of the unavoidable molecular damage), and everyone ends up somewhere different in that state space. All completely normal.
The only way to prevent and cure the parts of normal aging that we have defined to be age-related disease is to fix the causes of aging, because age-related diseases ARE aging. It is all the consequence of exactly the same processes at root. The three current views of what those causes are:
SENS: http://www.sens.org/research/introduction-to-sens-research
Hallmarks of Aging: http://dx.doi.org/10.1016/j.cell.2013.05.039
Seven Pillars: http://buckinstitute.org/CellCommentary