The research results for dementia look pretty dismal, especially since a fair number of studies have already been done.  The only area of hope is for mild cognitive impairment, a precursor to dementia. Even for mild cognitive impairment, the two large studies which have been done were only three months in duration.  

Dementia: Alzheimer's Disease: Acetyl-L-Carnitine Little or No Value in Large Study: In a very large DB PC study of 431 patients under 65 years old using ALCAR 3g/day vs. placebo, younger patients progressed a little more slowly in developing AD and ones older had dementia progress a little more rapidly. However, overall ALCAR did no better than placebo. A 1-year multicenter placebo-controlled study of acetyl-L-carnitine in patients with Alzheimer's disease. Thal LJ, Carta A, et al. UCSD, La Jolla, Neurol ’96;47:705

Dementia: Alzheimer's Disease: Acetyl-L-Carnitine No Help in Large Study: In a 1 year, 229-patient DB PC study, researchers found no value for probable Alzheimer's. Neurology 2000 Sep 26;55(6):805-10

Dementia: Alzheimer's Disease: Review Says No Reason to Recommend ALCAR:  In an analysis of all DB randomized trials (11) through Jan. 2003, all trials assessed the cognitive effects of ALCAR and in addition six considered severity of dementia, six considered functional ability and six considered clinical global impression (CGI). Treatment effects favored ALCAR at 12 and 24 weeks only for the Clinical Global Impression (CGI) [OR 2.33, P<0.01] and [OR 3.91, P=0.01] but not at 52 weeks. There was no evidence of benefit for ALCAR in the areas of cognition, severity of dementia, functional ability or Clinical Global Impression as a continuous measure. The reviewer notes that the couple positive findings might be chance findings in view of the large number of measures in the studies. Maudsley Hospital, London. Acetyl-L-carnitine for dementia. Hudson S, Tabet N. Cochrane Database Syst Rev. 2003;(2):CD003158. 

Dementia: Alzheimer's: Small Study Claims Minor Benefit: In a DB PC 6-month study of 30 mild-moderately demented adults, those on ALCAR had significantly less deterioration in timed cancellation tasks and Digit Span (forward) and a trend toward less deterioration in a timed verbal fluency task. No differences were found in any other neuropsychological test results. Sano M, Bell K, Cote L, et al. Double-blind parallel design pilot study of acetyl levocarnitine in patients with Alzheimer’s disease. Columbia University, Arch Neurol 1992;49:1137-41.

Dementia: Acetyl-L-Carnitine Not as Good as Alpha GPC: In a randomized study comparing  l-alpha-glyceryl- phosphorylcholine (alpha GPC) and ST200 (acetyl-l-carnitine) among 126 patients with probable senile dementia of Alzheimer's type (SDAT) of mild to moderate degree, the results showed significant improvements in most neuropsychological parameters in the alpha GPC recipients. Improvements with ALCAR were of a lesser extent. Multicentre study of l-alpha-glyceryl-phosphorylcholine vs ST200 among patients with probable senile dementia of Alzheimer's type. Parnetti L, Abate G, et al. University of Perugia, Italy. Drugs Aging. 1993 Mar-Apr;3(2):159-64

Dementia: ALCAR Said to Help in Small, Short Study: In a DB PC study of 60 mild Alzheimer's patients, those on ALCAR 2 g/day for 3 months showed statistically significant improvement in the behavioral scales, in the memory tests, in the attention barrage test and in the Verbal Fluency test. Acetyl-L-carnitine in the treatment of mildly demented elderly patients. Passeri M, Cucinotta D, et al, University of Parma, Italy. Int J Clin Pharmacol Res. 1990;10(1-2):75-9

Dementia: ALCAR Said to Help in Small, Short Study: In a DB PC study of 30 patients over 65 with mild mental impairment, those on acetyl-L-carnitine, 2 g/day for three months,  showed statistically significant improvement in the behavioral performances (Blessed Dementia Scale p less than 0.02; Stuard Hospital Geriatric Rating Scale p less than 0.01), in the memory tests (Rey short-term p less than 0.02; Rey long-term p less than 0.05; Corsi p less than 0.05), in the attention test (Barrage test p less than 0.01) and in the Verbal Fluency test p less than 0.01). Cucinotta D, Passeri M, Ventura S, et al. University of Perugia, Italy. Multicenter clinical placebo-controlled study with acetyl-L-carnitine (LAC) in the treatment of mildly demented elderly patients. Drug Development Res 1988;14:213-6.

Degenerative Cerebellar Ataxia: In this DB PC crossover study of 24 adults with degenerative cerebellar ataxia with all patients on ALCAR for 6 months and placebo for 6 months, both groups were said to improve. However, I couldn't figure out if they meant they improved on ALCAR or if ALCAR was no better than placebo. Sorbi S, Forleo P, Fani C, Piacentini S. Double-blind, crossover, placebo-controlled clinical trial with L-acetylcarnitine in patients with degenerative cerebellar ataxia. Clin Neuropharmacol 2000;23:114-8.

Dementia: ALCAR Not Significantly Better: In a small 6-month DB PC study of ALCAR 1 g/day for 20 of 36 Alzheimer's patients who completed the study, there were only several non-significant trends in favor of the ALCAR. Five patients did have some nausea and vomiting while on ALCAR. Rai G, Wright G, Scott L, et al. Double-blind, placebo controlled study of acetyl-L-carnitine in patients with Alzheimer’s dementia. London, England. Curr Med Res Opin 1990;11:638–47. 

Dementia Might Have Been Helped by ALCAR: In a small 12-week DB study of 24 patients with mild to moderate dementia cerebrovascular pathologies or major depression, piracetam was of no value, but ALCAR led to a significant improvement of the behavioral profile, of attention and of psychomotricity. Neuropsychological changes in demented patients treated with acetyl-L-carnitine. Sinforiani E, Iannuccelli M, et al. University of Pavia, Italy. Int J Clin Pharmacol Res. 1990;10(1-2):69-74. 

Dementia: ALCAR Helped Senile in Small Study: In a 40-day DB PC study of 40 senile elderly using ALCAR 1 g. three times a day, there was a significant improvement of the mental functioning without incidence of significant side effects. Study of the efficacy and tolerability of L-acetylcarnitine therapy in the senile brain. Bonavita E. Int J Clin Pharmacol Ther Toxicol. 1986 Sep;24(9):511-6.

Mild Cognitive Impairment Helped by ALCAR in Large Study: In a 5-month PC study of 236 mildly impaired elderly, 90 days of ALCAR at 1.5 g/day increased all measures of cognitive functioning, especially memory and constructive thinking, and of emotional-affective state and on some scores of the relational behavior. Effects of L-acetylcarnitine on mental deterioration in the aged: initial results. Cipolli C, Chiari G. Clin Ter. 1990 Mar 31;132(6 Suppl):479-510.

Mild Cognitive Impairment: L-Acetylcarnitine Helped Elderly Mental Functioning and Depression in Large Study: In a single-blind PC study of 481 elderly given 30 days of placebo, 90 days of L-acetylcarnitine (LAC) 1500 mg/day and 30 more days of placebo, the MMSE increased with LAC treatment (p < 0.0001). The Randt Memory Test also revealed that LAC the total score and the memory index increased significantly. Some benefit persisted after LAC was discontinued. The Geriatric Depression Scale and Hamilton Depression scores also improved (p < 0.0001). The Family Stress Scale showed a significant decrease after treatment (p < 0.0004). No significant adverse drug reactions occurred. L-acetylcarnitine treatment of mental decline in the elderly. Salvioli G, Neri M. University of Modena, Italy. Drugs Exp Clin Res. 1994;20(4):169-76.