StoneColdNTO
Administrator
Summarized by Robert W. Griffith, MD
March 26, 2004
Introduction
Testosterone levels tend to decrease in men, gradually, as they get older. It's been suggested that this may be a reason for a lessened interest in sex and a greater risk of depression, at least in some cases. Now a study has been reported in the journal Neurology that implicates low testosterone levels in men with an increased risk of developing Alzheimer's disease. It should be noted that there's quite a lot of evidence already that hormone changes in women are related to a similar risk.
What was done
Men who volunteered for the Baltimore Longitudinal Study of Aging since 1958 were studied. Their ages varied between 32 and 87 on entry into the study, and they were free of Alzheimer's disease at that time. They were followed carefully for an average of 19 years, and had repeated blood sampling during that period.
Some of the testosterone in the blood is combined with a protein and is therefore less relevant than the so-called 'free' testosterone. Blood levels of testosterone, in both its total and free form, were estimated in the samples, along with the combining protein, sex hormone binding globulin (SHBG). The relative amount of free testosterone was expressed as a proportion of the total testosterone, and called the free testosterone index (FTI).
Every two years the participants had various screening tests of their mental ability, and anyone with positive findings was examined in depth to see if he actually had Alzheimer's.
What was found
There were 54 cases of Alzheimer's diagnosed during the study. These men were roughly 7 years older than the men without Alzheimer's. The total testosterone and SHBG levels were not different in the Alzheimer's patients from those in the remaining participants, either at baseline or in the last blood sample taken.
The average FTI scores showed little difference in the Alzheimer's patients. However, when the individual FTI values were analyzed, it was clear that there was indeed a link; increases in FTI were associated with a decrease in likelihood of Alzheimer's. The term 'hazards ratio' (HR) was used to describe this: those with an increased FTI had an HR of 0.41, i.e. they were 0.41 times as likely to develop Alzheimer's.
To make sure there was a real relationship between FTI and Alzheimer's, adjustments were made to allow for differences in age, smoking, level of education, body weight, diabetes, any cancer diagnosis, and hormone supplements.
Even after such allowances, the HR for those with increased FTI was still significant at 0.67, i.e. these subjects were 0.67 times as likely to develop Alzheimer's as those with 'average' FTI levels.
Comment
The results of these analyses are at first a little hard to understand, as they are reported 'the wrong way round'. In fact, it should be clear that low free testosterone levels are linked to an increased risk of Alzheimer's disease. Moreover, the change (i.e. lower free testosterone) appeared before the diagnosis of Alzheimer's. This suggests it's related to the cause, rather than being an effect of the disease.
Of course, the next question is whether administering testosterone supplements can protect older men against getting Alzheimer's. That's something that will require prospective clinical studies; it's necessary to evaluate carefully any benefits of testosterone therapy against the risks that it carries - these include the possibility of prostate cancer, an enlarged prostate (prostatism), excess red blood cells, and sleep apnea. So don't rush to get a testosterone patch, just yet!
Source
Free testosterone and risk for Alzheimer disease in older men. SD. Moffat, AB. Zonderman, EJ. Metter, et al., Neurology, 2004, vol. 62, pp. 188--193
March 26, 2004
Introduction
Testosterone levels tend to decrease in men, gradually, as they get older. It's been suggested that this may be a reason for a lessened interest in sex and a greater risk of depression, at least in some cases. Now a study has been reported in the journal Neurology that implicates low testosterone levels in men with an increased risk of developing Alzheimer's disease. It should be noted that there's quite a lot of evidence already that hormone changes in women are related to a similar risk.
What was done
Men who volunteered for the Baltimore Longitudinal Study of Aging since 1958 were studied. Their ages varied between 32 and 87 on entry into the study, and they were free of Alzheimer's disease at that time. They were followed carefully for an average of 19 years, and had repeated blood sampling during that period.
Some of the testosterone in the blood is combined with a protein and is therefore less relevant than the so-called 'free' testosterone. Blood levels of testosterone, in both its total and free form, were estimated in the samples, along with the combining protein, sex hormone binding globulin (SHBG). The relative amount of free testosterone was expressed as a proportion of the total testosterone, and called the free testosterone index (FTI).
Every two years the participants had various screening tests of their mental ability, and anyone with positive findings was examined in depth to see if he actually had Alzheimer's.
What was found
There were 54 cases of Alzheimer's diagnosed during the study. These men were roughly 7 years older than the men without Alzheimer's. The total testosterone and SHBG levels were not different in the Alzheimer's patients from those in the remaining participants, either at baseline or in the last blood sample taken.
The average FTI scores showed little difference in the Alzheimer's patients. However, when the individual FTI values were analyzed, it was clear that there was indeed a link; increases in FTI were associated with a decrease in likelihood of Alzheimer's. The term 'hazards ratio' (HR) was used to describe this: those with an increased FTI had an HR of 0.41, i.e. they were 0.41 times as likely to develop Alzheimer's.
To make sure there was a real relationship between FTI and Alzheimer's, adjustments were made to allow for differences in age, smoking, level of education, body weight, diabetes, any cancer diagnosis, and hormone supplements.
Even after such allowances, the HR for those with increased FTI was still significant at 0.67, i.e. these subjects were 0.67 times as likely to develop Alzheimer's as those with 'average' FTI levels.
Comment
The results of these analyses are at first a little hard to understand, as they are reported 'the wrong way round'. In fact, it should be clear that low free testosterone levels are linked to an increased risk of Alzheimer's disease. Moreover, the change (i.e. lower free testosterone) appeared before the diagnosis of Alzheimer's. This suggests it's related to the cause, rather than being an effect of the disease.
Of course, the next question is whether administering testosterone supplements can protect older men against getting Alzheimer's. That's something that will require prospective clinical studies; it's necessary to evaluate carefully any benefits of testosterone therapy against the risks that it carries - these include the possibility of prostate cancer, an enlarged prostate (prostatism), excess red blood cells, and sleep apnea. So don't rush to get a testosterone patch, just yet!
Source
Free testosterone and risk for Alzheimer disease in older men. SD. Moffat, AB. Zonderman, EJ. Metter, et al., Neurology, 2004, vol. 62, pp. 188--193
