For thousands of years, the people of China, Japan, India, and Thailand have consumed green tea and used it medicinally to treat everything from headaches to heart diseases. Over the past few decades, however, research in both Asia and the West have taken place providing scientific evidence of green tea’s numerous health benefits. As a whole, studies indicate that regular consumption of green tea may slow or prevent conditions including high cholesterol, heart disease, arthritis, impaired immune disease and liver disease. In yet another recent study on the beverage’s healthful properties, published in the academic journal Phytomedicine, researchers have found evidence that enzymes in the drink may help in fighting Alzheimer’s and other forms of dementia.
Researchers at the Newcastle University have also found that the Chinese brew may also play a vital role in guarding against cancer. The Newcastle team focused on whether or not once the tea was in the digestive system if the protective properties were still as effective. “What was really exciting was that we found when green tea is digested, the resulting chemicals are actually more effective against key triggers of Alzheimer’s,” said Ed Okello, from the university’s School of Agriculture, Food and Rural Development. “The digested compounds also had anti-cancer properties, significantly slowing down the growth of tumour cells which we were using in our experiments,” Okello said.
Previous studies have shown that polyphenols, present in black and green tea, bind with the toxic compounds and protect brain cells. When ingested, the polyphenols are broken down to produce a mix of compounds and it was these the team tested in their research. According to Okello, there are many factors that together have an influence on diseases such as cancer and dementia – a good diet, plenty of exercise and a healthy lifestyle are all important. “But I think it’s fair to say that at least one cup of green tea a day may be good for you and I would certainly recommend it,” he added.
The study involved participants in the Chicago Health and Aging Project, a longitudinal study of risk factors for Alzheimer's disease involving a population of older adults on Chicago's south side. At three year intervals, the entire population completed a brief self-report measure of depressive symptoms and clinical evaluations for Alzheimer's disease.
Initial analyses focused on a group of 357 individuals who developed Alzheimer's disease during the course of the study. The study found a barely perceptible increase in depressive symptoms, a rate of 0.04 symptoms per year, during six to seven years of observation before the diagnosis of Alzheimer's disease and no change during two to three years of observation after the diagnosis.
Because dementia may reduce the accuracy of self-report, in a subgroup of 340 participants, researchers conducted additional analyses of change in depressive symptoms by interviewing family, friends and other who were close to the study participants. Neither Alzheimer's disease nor its precursor, mild cognitive impairment, was associated with change in depressive symptoms during a mean of three years of observation.
The results were consistent across all demographics. There was no evidence that sex, age, education or race modified the trajectory of depressive symptoms before or after Alzheimer's disease was diagnosed.
“Here is this terrible disease that robs people of who they are and their ability to function and yet it doesn't make them depressed,” said Wilson. “Alzheimer's may disrupt the ability to have prolonged bouts of negative emotions, in much the same way it disrupts many other activities.”
The study authors suggest additional studies of patients with Alzheimer's disease for longer periods to determine if depressive symptoms may eventually decrease as the disease becomes more severe.
In addition, researchers at Rush continue to look at why depression increases the risk of Alzheimer's disease.
The study was supported by funding from the National Institutes of Health (NIH)/ National Institute on Aging (NIA). Co-authors include G.M. Hoganson, BS; K.B. Rajan, PhD; L.L. Barnes, PhD; C.F. Mendes de Leon, PhD; and D.A. Evans, MD.
The prospective Rotterdam Study involved 5,395 people over age 55 with no dementia at baseline. All of the participants, who lived in one section of the Rotterdam area, provided dietary information when the study began in 1990.
The researchers previously reported a similar association of vitamin E intake with a lower risk of dementia and Alzheimer's disease over six years of follow-up among the cohort.
The current study found that after 9.6 years of follow-up, 465 of the participants had developed dementia; 365 of these cases were classified as Alzheimer's disease.
Higher baseline vitamin E consumption correlated with lower long-term risk of dementia in models minimally adjusted for age only and those adjusted for age, education, apolipoprotein genotype, total caloric intake, alcohol and smoking habits, body mass index, and use of supplements (both P=0.02 for trend).
Dietary surveys indicated that margarine was by far the biggest contributor to vitamin E intake at 43.4%, followed by sunflower oil at 18.5%, butter at 3.8%, and cooking fats at 3.4%.
Participants with vitamin E intakes in the top third, averaging 18.5 mg per day, were 25% less likely to develop dementia of any kind over almost 10 years of follow-up than those in the bottom third, who averaged only 9.0 mg per day. Higher baseline vitamin E consumption correlated with lower long-term risk of dementia (both P=0.02 for trend).
While the top versus bottom tertile comparison was significant, the middle group with vitamin E intake averaging 13.5 mg per day was no less likely to develop dementia than the lowest intake group.
For Alzheimer's disease alone, the multivariate-adjusted risk was 26% lower among those with the highest intake compared with the lowest (95% confidence interval 3% to 44%, P=0.03 for trend). But intermediate intake again appeared to have no impact.
Other antioxidants — vitamin C, beta-carotene, and flavonoids — held no significant associations with dementia or Alzheimer's disease risk (multivariate adjusted P=0.50 to >0.99 for trend).
Sensitivity analyses excluding participants who reported taking supplements at baseline showed similar results.
The researchers noted that the vitamin intakes seen in the study were consistent with a typical Western diet but cautioned about the possibility of residual confounding in the observational results.
Of the participants, 15.5%, 29.7%, 28.1%, and 21.1% reported being physically inactive at teenage, at 30 years, at 50 years, and in late life respectively; the increase in cognitive impairment for those who were inactive was between 50% and 100% at each time point. When physical activity measures for all four ages were entered into a single model and adjusted for variables such as age, education, marital status, diabetes, hypertension, depressive symptoms, smoking, and BMI, only teenage physical activity status remained significantly associated with cognitive performance in old age.
Middleton added, “As a result, to minimize the risk of dementia, physical activity should be encouraged from early life. Not to be without hope, people who were inactive at teenage can reduce their risk of cognitive impairment by becoming active in later life.”
The researchers concluded that the mechanisms by which physical activity across the life course is related to late life cognition are likely to be multi-factorial. There is evidence to suggest that physical activity has a positive effect on brain plasticity and cognition and in addition, physical activity reduces the rates and severity of vascular risk factors, such as hypertension, obesity, and type II diabetes, which are each associated with increased risk of cognitive impairment.
“Low physical activity levels in today's youth may mean increased dementia rates in the future. Dementia prevention programs and other health promotion programs encouraging physical activity should target people starting at very young ages, not just in mid- and late life,” said Middleton.
People with mild cognitive impairment can be affected by a reduction in their ability to think, such as reduced memory and a short attention span.
“We wanted to find out whether highly educated patients with mild cognitive impairment differed in terms of tolerance of the disease from patients with intermediate and low levels of education,” says Rolstad.
By analysing the patients' spinal fluid, the researchers were able to examine whether there were signs of dementia in the brain.
“Highly educated patients with mild cognitive impairment who went on to develop dementia over the next two years had more signs of disease in their spinal fluid than those with intermediate and low levels of education,” says Rolstad.
Despite having more disease in the brain, the highly educated patients showed the same symptoms of the disease as their less well educated counterparts. This means that patients with higher levels of education tolerate more disease in the brain.
The researchers also studied patients with mild cognitive impairment who did not go on to develop dementia over the next two years.
“We found that the highly educated patients who did not develop dementia during the course of the study showed signs of better nerve function than those with lower levels of education,” says Rolstad. “This finding means that the highly educated not only tolerate more disease in the brain but also sustain less nerve damage during the early stages of the disease.”
The results indicate that a higher reserve capacity delays the symptoms of dementia and the progress of the disease. This can help the care sector to be more aware of dementia in highly educated patients, and thus increase the chances of the correct treatment being given.
Researchers from Boston University School of Medicine determined that excess abdominal fat places otherwise healthy, middle-aged people at risk for dementia later in life. Preliminary findings suggest a relationship between obesity and dementia that could lead to promising prevention strategies in the future. Results of this study are published early online in Annals of Neurology, a journal of the American Neurological Association.
A 2005 World Health Organization (WHO) report estimated that 24.3 million people have some form of dementia, with 4.6 million new cases annually. Individuals with dementia exhibit a decline in short-term and long-term memory, language processing, problem solving capabilities, and other cognitive function. Clinical diagnosis of dementia is made when two or more brain functions are significantly impaired. Symptoms of dementia can be attributed to irreversible causes such Alzheimer's disease, vascular dementia, and Huntington's disease, or caused by treatable conditions such as brain tumor, medication reaction, or metabolic issues.
For the current study, Sudha Seshadri, M.D. and colleagues recruited participants from the Framingham Heart Study Offspring Cohort. The sample included 733 community participants who had a mean age of 60 years with roughly 70% of the study group comprised of women. Researchers examined the association between Body Mass Index (BMI), waist circumference, waist to hip ratio, CT-based measures of abdominal fat, with MRI measures of total brain volume (TCBV), temporal horn volume (THV), white matter hyperintensity volume (WMHV) and brain infarcts in the middle-aged participants.
“Our results confirm the inverse association of increasing BMI with lower brain volumes in older adults and with younger, middle-aged adults and extends the findings to a much larger study sample,” noted Dr. Seshadri. Prior studies were conducted in cohorts with less than 300 participants and the current study includes over 700 individuals.
“More importantly our data suggests a stronger connection between central obesity, particularly the visceral fat component of abdominal obesity, and risk of dementia and Alzheimer's disease,” Dr. Seshadri added. The research showed the association between VAT and TCBV was most robust and was also independent of BMI and insulin resistance. Researchers did not observe a statistically significant correlation between CT-based abdominal fat measures and THV, WMHV or BI.
“Our findings, while preliminary, provide greater understanding of the mechanisms underlying the link between obesity and dementia,” concluded Dr. Seshadri. “Further studies will add to our knowledge and offer important methods of prevention.”
Source: Stéphanie Debette, Alexa Beiser, Udo Hoffmann, Charles DeCarli, Christopher J. O'Donnell, Joseph M. Massaro, Rhoda Au, Jayandra J. Himali, Philip A. Wolf, Caroline S. Fox, Sudha Seshadri. Visceral Fat is Associated with Lower Brain Volume in Healthy Middle-Aged Adults. Annals of Neurology, 2010