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Sex Differences in Brain Aging

Analysis post mortem and in vivo imaging reports have demonstrated that ageing is associated with decreased brain tissue size and increased brain cerebrospinal fluid (CSF) volume. Eduard Coffey and al in this study have used MR imaging morphometry to examine the effects of sex on age related changes in the size of regional brain matter and CSF spaces in elderly volunteers living independently. The assumption of this analysis is that these changes are more important in men than in women. The authors have considered 330 elderly (age range 66-96 years), 129 men and 201 women; all the subjects have been selected from among participants in the Cardiovascular Health Study (CHS). Brain MR imaging has been performed in all subjects and the following regions have been defined for volume measurement: intracranial volume, cerebral hemisphere volume, lateral ventricle volume, third ventricle volume, peripheral (sulcal) CSF volume, lateral (sylvian) fissure CSF volume, frontal region area, temporoparietal region area, parieto-occipital region area, intracranial area.
The authors have demonstrated changes between men and women also in some areas:

  • peripheral CSF volume: the regression coefficient is 2.11 for men but only 0.06 for women (P<0.03). At age 65 years, men have a mean peripheral CSF volume about 5.70 mL smaller than that of women, but at age 95 years, men have a mean peripheral CSF volume about 55.67 mL larger than women.
  • lateral fissure CSF volume: the regression coefficient is 0.23 for men but only 0.10 for women (P<0.04). at age 65 years, men have a mean lateral fissure volume about 0.80 mL larger than that of women, but at age 95 years, this difference increased to 4.86 mL.
  • parieto-occipital region area: the regression coefficient is -0.31 for men but only -0.09 for women (P<0.03). At the age 65 years, men have a mean parieto-occipital region area about 2.15 cm2 larger than that women, but at age 95 years, men have a mean parieto-occipital region area about 4.54 cm2 smaller than that of women.

In the other brain regions examined main effects of age has been observed, but they are similar in men and women. The authors in this study have demonstrated some differences, but also properly they underline some limits of this study: 1) health status of the subjects examinated, infact probably they may be healthier than the population, this fact is due to the selection criteria for the CHS; 2) the analyses of brain size have been restricted to the axial plane, because 3-dimensional reconstruction is not possible without loss of resolution; 3) the use of two different scanners to determine the brain size. The neurobiological bases and functional correlates of these sex differences require others studies.