Let's use some criteria from Diseased thinking: dissolving questions about disease (http://lesswrong.com/lw/2as/real_diseases_unasking_the_quest...).

1. Biological? Yes

2. Involuntary? Yes

3. Rare? No

4. Unpleasant? Yes

5. Discrete? No

6. Medicable? Yes

So aging has many aspects of what we call disease. Of course, the implied question that everyone cares about is is, "Will humanity be better off if we devote more resources to curing aging?" The answer to that brings much more baggage, and depends on your moral and religious views.