My father died when I was 18, seven years ago, when I was a freshman in college. That’s when the dementia had destroyed enough of his brain to destroy the man I knew as my father. Dad was a laid-back sort of guy, with a sweet smile and an easy sense of humor. He loved music and technology and boats, was a championship marksman, enjoyed exotic foods and made holiday pies. He built a playhouse for my sister and myself, a shelter for the dog, racks for the firewood. We went hiking and backpacking together and took a family vacation across America.

The doctors can’t say when the disease arrived. But by the time I was halfway through that first year of college, it had stolen my dad and left a silent, sullen man in his place. He spent more and more time playing computer card solitaire games, and he took no interest in what I might be doing now that I wasn’t living at home. Our phone conversations were filled with empty silences.

The images from last month’s brain scans show many empty places, fingers of blackness where his personality used to be and a gaping hole were the words he used to know were stored. The dementia has consumed the tissue of this once above-average brain, leaving vacant holes filled with fluid behind an expressionless face. Leaving my family with the knowledge that whatever advances are made in Alzheimer’s and dementia research, they will come too late for my dad to ever know his grandchildren. Leaving me with the fear that the failure in his brain is genetic and that dementia will start destroying me.

Yesterday we visited the neurologist. He was quietly sympathetic as he showed us the MRI images and discussed where we might be in the progress of the disease. He seemed almost apologetic that there is nothing to be done. It may be three years yet before we start to see physical manifestations of his shrinking brain: loss of motor control, incontinence, difficulty swallowing. In the meantime, my father will become more clueless, more inarticulate, and more difficult to be around. But it won’t be over until his saliva gets in his lungs and he develops pneumonia or until the instructions to keep his heart beating disappear. The end of this chapter could still be 10 years away.

I stopped myself before I asked the neurologist if there was any way we could speed up the disease. Instead I watched Mom’s hands. At 52, her hands are starting to look like her father’s, who is 79. She is aging before her time because although my dad is dead, we can’t bury my father.

I am angry at the dementia, but I can’t scream at it, I can’t reason with it, and I can’t ignore it. It’s just there, self-satisfied and taking up the entire living room like some monster-cat on steroids, impervious to temper tantrums and contentedly shedding fur to be tracked through the rest of the house. I hate it for killing Dad, for aging Mom, for having an immediate impact on the lives and bodies of people it doesn’t inhabit. I hate it for moving so slowly. I hate how much of my life will be lost by the time it’s done and how much my family has already lost. I hate that I want to postpone any children I might have until after the funeral, since what’s left of my father will never understand and since I would rather my children grow up with stories of how their grandfather was instead of memories of how he is now.

I am angry, but there is nothing for me to yell at that would make any difference.