Bear in mind that they say "coenzyme Q10 works by improving the function of mitochondria"
if this is so then it's reasonable to suppose that as Alzheimer's is also a condition resulting from mitochondrial dysfunction
then it may also slow the progression and maybe help slow AD.
It's also worth remembering that one of the effects of Statin therapy is to lower your body's coenzyme Q10 level so I'm sure you can all work out what impact the use of statins is likely to have on Parkinsons/Alzheimer's disease incidence. Still it all makes work/money for big pharma.
I should perhaps remind readers that this research was done in 2002 and there haven't been many follow ups although some may be ongoing, It's also likely that coenzyme Q10 and creatine work in synergy with each other to provide more neuroprotection than each on it's own. I can't see how any brain can function without optimum supplies of vitamin D, omega 3 melatonin and magnesium so I would predict that ensuring all the above mentioned supplements would be required by most people with a Parkinson's/Alzheimer's diagnosis. Melatonin in particular is the prime agent for mitochondrial protection and is as likely to be deficient in the elderly as vitamin D3.