Some observational studies suggested a link between brain levels of aluminum and Alzheimer's disease . Since the association was found, many studies have investigated whether aluminum increases the risk for Alzheimer's. The findings are far from clear. Several meta-analyses examined the association between aluminum levels in drinking water and dementia risk, and the evidence is mixed and inconclusive   .
It found that levels of aluminum consumption in drinking water in excess of 0. Of the remaining 13 moderate quality studies, 6 found an association between higher aluminum levels in drinking water and increased dementia risk  , 4 found no associations  , and 1 found a protective effect of higher soil levels of aluminum .
Other elements present in drinking water, such as fluoride, copper, zinc, or iron, could also affect cognitive function and the results of these studies . Some antacids contain high levels of aluminum, as aluminum hydroxide reduces stomach acidity. A very large meta-analysis of 9 observational studies including more than 6, people reported that regular antacid use was not associated with Alzheimer's disease . Even when the analysis was confined to people who used antacids regularly for over 6 months, there was no association with Alzheimer's.
Studies with longer follow-up may be needed to definitively exclude the association between antacid use and dementia risk. Aluminum salts in antiperspirants dissolve into the skin's surface and form a temporary barrier within sweat ducts, which stops the flow of sweat to the skin's surface.
No studies have directly examined the link between aluminum-containing antiperspirant use and Alzheimer's risk. However, a few studies have evaluated the link between antiperspirant use and breast cancer. Two studies found no increase in breast cancer risk   , but one other study reported that patients who used antiperspirant products more frequently and longer on shaved underarms were diagnosed with breast cancer at an earlier age . Studies show that aluminum salts in antiperspirants are poorly absorbed by the body, and the little that is absorbed is flushed out by the kidneys  .
However, if you regularly shave with a razor, aluminum may be more readily absorbed via small nicks and abrasions.
To limit potential risks, avoid application of antiperspirants shortly after shaving and limit excessive use. A meta-analysis of 3 observational studies including more than 1, people reported that occupational aluminum dust exposure was not associated with Alzheimer's . Note: Content may be edited for style and length. Science News. Story Source: Materials provided by Keele University. ScienceDaily, 12 February Keele University. Elevated brain aluminium, early onset Alzheimer's disease in an individual occupationally exposed to aluminium.
Retrieved September 25, from www. Alzheimer's disease is the sixth leading cause of death among in older adults. The exact causes of Alzheimer's It did not seem necessary to adjust for occupation after having adjusted for education level. However, the model with aluminum in two classes was slightly better than that in which aluminum was a continuous variable Akaike criterion: 2, The pH level was not associated with dementia, and the interaction between aluminum and pH was not significant.
Could Exposure To Aluminum Cause Alzheimer's Disease?
Analyses performed on the sample of 2, nondemented subjects at baseline, for whom components of drinking water and covariates were available. Nonparametrically adjusted for age and gender and parametrically adjusted for educational level, wine consumption, and place of residence. Analyses restricted to cases classified as Alzheimer's disease cases also suggested a deleterious effect of high aluminum concentrations and a protective effect of high silica concentrations on the risk of Alzheimer's disease table 5.
These effects were not significant for other types of dementia 71 cases , although the relative risks were of the same order. This may be explained by a lack of power in the latter analysis.
Analyses performed on the sample of 2, nondemented subjects at baseline for whom components of drinking water and covariates were available. The observations are summarized in table 6. Among the exposed subjects, the expected number of demented cases, using the Cox model adjusted for covariates 27 , was computed to be 8.
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Expected number calculated with Martingale residuals, nonparametrically adjusted for age and gender and parametrically adjusted for educational level, wine consumption, and place of residence. Information about mineral water consumption was collected for 1, nondemented subjects seen at the 3-year follow-up for whom covariates were available; subjects developed dementia including 88 Alzheimer's disease cases between the 3- and the 8-year follow-up.
Could Exposure To Aluminum Cause Alzheimer's Disease?
In this subsample, 48 percent of the subjects were classified as daily drinkers of mineral water. The analysis of this subsample, adjusted for age, gender, educational level, wine consumption, place of residence, and silica yielded a relative risk of 2. This relative risk reached 3. There was no evidence of a significant interaction between aluminum and mineral water consumption. In this subanalysis, after adjustment for educational level, wine consumption, place of residence, and aluminum, the relative risk for silica was estimated to be 0.
In the analyses, we considered as exposed all the subjects living in parishes with high levels of aluminum. An alternative was to consider subjects who drank daily mineral water as nonexposed; in this case, the effect of aluminum still remained unchanged and was still significantly associated with dementia.
The results of the sensitivity analyses on the n. The sensitivity analyses on n. The effect of silica was also changed slightly in these sensitivity analyses, and it was no longer significant in the fourth assumption, i. Analyses performed on 3, subjects: 2, were followed effectively at least once, and subjects refused the follow-up procedure. Analyses performed on 3, subjects: 2, were followed effectively at least once and subjects died before any follow-up evaluation.
This result is highly significant despite the small number of subjects exposed to such levels. No dose-response relation was apparent in the analyses. Although this weakens the plausibility that aluminum has a causal effect on Alzheimer's disease, the interpretation may also be that there is a threshold effect around 0. Subjects who refused to participate in the follow-up 31 or who died are probably more likely to be demented.
In our study, the percentages of deaths before any follow-up visit and refusals before any follow-up visit were slightly higher for subjects exposed to aluminum, but this difference was not significant, which makes such a bias unlikely. The effect of aluminum estimated in the sensitivity analyses appeared to be somewhat lower than that calculated from the study table 4 , model 5.
Nonetheless, all these sensitivity analyses suggest that the main result is robust. Since the number of demented subjects exposed to high levels of aluminum was low, our results could be sensitive to a misdiagnosis of demented subjects. Therefore, in an additional analysis, we chose to define as demented the subjects who screened positive in the first stage of the diagnostic procedure. Among these, of whom 21 exposed to aluminum were considered as demented by the new definition. Therefore, it is unlikely that the apparent effect of aluminum comes from a misclassification of the subjects.
In our analyses, Alzheimer's subjects were classified as those with probable or possible Alzheimer's disease. To increase the specificity of the analyses, another analysis was performed that considered only the 89 probable Alzheimer's disease cases, including six exposed subjects. Of course, when studying the effects of risk factors in an old population, it must be remembered that the subjects are highly selected because they are still alive and have not developed the disease. Selection in a heterogeneous population may produce apparent effects that are different from true effects, as shown by Aalen One way of partially coping with this problem is to adjust on explanatory variables that may explain part of the heterogeneity.
This is why, in an additional analysis, we adjusted for baseline cognitive status, which is a good predictor of dementia and Alzheimer's disease. Controlling this baseline heterogeneity did not modify the relative risks for aluminum and silica.
The Paquid survey design incorporates a grouping of the participants into parishes, and this may induce a correlation of the observations. It is thus not to be excluded that some unmeasured environmental factor shared by the members of the same parish could play a confounding role. Analysis of dependent survival data by the classical Cox proportional hazard model using conventional partial likelihood methods may underestimate the variance of regression coefficients specific to each group, leading to incorrect inferences.
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In the frailty model, the hazard function depends partly on an unobservable random variable a random effect thought to act multiplicatively on the hazard. A large value of the variance of the random effects means closer positive relation between the subjects of the same parish and a greater heterogeneity between the groups.
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Aluminum and Alzheimer's disease: after a century of controversy, is there a plausible link?
The macro did not allow left truncated data, so we analyzed the delay between the time of entry into the cohort and the time of censorship or the time of outcome and then adjusted for age at entry. This means we may admit that there is no intragroup correlation in our sample or that such a correlation is weak. The relative risks for aluminum and silica were unchanged, but the standard errors of these regression coefficients were slightly increased. Several investigators have described how the pH of drinking water may affect the solubility of aluminum components It is plausible that the biological availability of aluminum is higher for low pH than for high pH, which would lead to an interaction between pH and aluminum.
These results were not confirmed in our study; nevertheless, Surface waters lakes or rivers are often treated with aluminum sulphate to induce flocculation and remove organic and other contaminants.