Wednesday November 24 2010
The study featured a test of dexterity, not intelligence
“Hormone replacement therapy can make a woman’s mind sharper,” according to the Daily Mail. The newspaper says that women taking hormone replacement therapy (HRT) performed better in tasks involving fine motor co-ordination skills than women of a similar age who were not taking HRT.
The story is based on a study that compared the results of finger-tapping tests in 33 menopausal women taking HRT with those of 26 menopausal women who had not used the therapy. Women not taking HRT showed less asymmetry between the performance of their left and right hands when performing simple tapping with the index finger, but more asymmetry between hands when performing a more complex sequential tapping task. The opposite findings were seen in women on HRT, a pattern that researchers say is normally observed in younger women.
Although these study findings shed some light on the possible effects of hormones upon brain activity, they have limited clinical implications. All of the women of this study were of comparable dexterity, and this single, experimental test of motor function in a small group of women does not provide much insight into whether their everyday lives were affected. Notably, despite what the press coverage has implied, this study has not investigated cognitive ability or intelligence and provides no evidence that HRT will give women “sharper minds” or boost IQ.
Where did the story come from?
The study was carried out by researchers from Durham University and was funded by grants from the Deutsche Forschungsgemeinschaft research foundation. The study was published in the peer-reviewed scientific journal Hormones and Behavior.
The headline featured in the Daily Mail is misleading in saying that HRT makes a woman’s mind “sharper” as the study only examined differences in hand tapping in a small sample of women. The body of the Mail’s story is representative of the research. The Daily Mirror, however, is completely incorrect in saying that HRT “boosts brain power”. This is not the conclusion of this research.
What kind of research was this?
There is a theory that activity in the right and left sides of the brain is affected by age, and that hormone manipulation can also have an effect. In this study, the researchers were specifically investigating whether HRT therapy affected “functional cerebral asymmetries” (FCAs), i.e. performance differences between the dominant and non-dominant hands when carrying out functional activities such as simple movement tasks. The experimental research was in older women taking HRT (two types were tested) and women not taking HRT.
Results of this type of study are of general scientific interest and shed some light on the possible effects of hormones upon brain activity. However, they have limited clinical application and provide limited information on the cognitive and functional abilities of women on hormone therapy or not.
What did the research involve?
The research recruited 62 postmenopausal women aged 46–71 who were put into three groups: women who had gone through menopause at least one year ago and had not used any HRT (26 women); women using continuous oestrogen HRT (15 women) and women using combined oestrogen and progestogen HRT (21 women). All were right-handed with good sight and normal dexterity. All groups were of the same educational level and there was no difference in the number of years since menopause.
The researchers used saliva samples to measure the participants’ oestrogen and progesterone levels. They then performed a finger-tapping task involving an apparatus consisting of four small, movable switches mounted on a metallic plate. The switches were positioned under each participant’s index, middle, ring and little finger. In the first test participants had to repeatedly tap the switch with the index finger as quickly as possible, and in the “sequential” test they had to repeatedly press buttons in the sequence of index finger, ring finger, middle finger, little finger. Participants repeated each test five times with each hand, and each 10-second trial was followed by a short break.
The mean tapping rate was calculated as the mean number of correct taps across the five trials. Manual asymmetry was calculated as the ratio of the differences between hands to overall performance (dominant and non-dominant hand).
What were the basic results?
A total of 59 women were included in the analysis after the exclusion of three participants in the HRT groups who had unusually low blood hormone levels. The basic findings were that postmenopausal women who were not taking HRT had little asymmetry between their right and left hands on simple (repetitive) finger-tapping. However, in sequential finger-tapping there was greater asymmetry, with better performance from their dominant hand.
In comparison, women on HRT (both types) demonstrated a lesser degree of asymmetry between hands when performing sequential finger-tapping. However, they demonstrated increased asymmetry when performing simple finger-tapping. Performance was related to oestrogen levels, with participants with higher oestrogen levels having greater asymmetry on simple tapping.
How did the researchers interpret the results?
The researchers conclude that their results suggest that HRT, and oestrogen therapy in particular, has a positive effect on the motor system and counteracts the changes normally seen with increasing age.
The researchers found that older women not taking HRT displayed less asymmetry when performing simple tapping, but asymmetry between hands when performing more complex sequential tapping with fingers. This, they suggest, reflects age-related changes in connectivity between motor areas of the brain. The opposite findings in women on HRT are, as they say, what has normally been observed when testing younger women (notably, no younger women were included in this study).
There are some limitations to this study, such as the small number of participants and the fact that women were not randomly assigned to the HRT or non-HRT groups, meaning that the results may have been affected by differences between the groups other than their use of HRT.
Although these study findings are of general scientific interest and shed some light on the possible effects of hormones upon brain activity, they have limited clinical implications. All of the women in this study were of comparable dexterity, and this small test of motor function in 33 menopausal women on HRT and 26 women not on HRT provides very limited information on their functional capacity. Despite its misleading news headlines, this study has not investigated cognitive ability and provides no evidence that women on HRT have sharper minds or higher IQ.