The study involved 74 non-smokers with amnestic MCI (average age 76), of whom half were given a nicotine patch of 15 mg a day for six months and half received a placebo. Cognitive tests were given at the start of the study and again after three and six months.
After 6 months of treatment, the nicotine-treated group showed significant improvement in attention, memory, speed of processing and consistency of processing. For example, the nicotine-treated group regained 46% of normal performance for age on long-term memory, whereas the placebo group worsened by 26%.
Nicotine is an interesting drug, in that, while predominantly harmful, it can have positive effects if the dose is just right, and if the person’s cognitive state is at a particular level (slipping below their normal state, but not too far below). Too much nicotine will make things worse, so it’s important not to self-medicate.
Nicotine has been shown to improve cognitive performance in smokers who have stopped smoking and previous short-term studies with nicotine have shown attention and memory improvement in people with Alzheimer's disease. Nicotine receptors in the brain are reduced in Alzheimer’s brains.
Because the dose is so crucial, and the effects so dependent on brain state (including, one assumes, whether the person has been a smoker or not), more research is needed before this can be used as a treatment.
(2012). Nicotine treatment of mild cognitive impairment.
Neurology. 78(2), 91 - 101.