Bioavailable testosterone is associated with a reduced risk of amnestic mild cognitive impairment in older men.
OBJECTIVE
We investigated the risk of amnestic mild cognitive impairment (aMCI) in relation to serum bioavailable (BT) and total testosterone (TT) levels in older men.


METHODS
A cross-sectional study in an ambulatory setting, with older men aged 55-93 years with normal cognition, aMCI and Alzheimer's disease (AD).


METHODS
Morning serum BT and TT levels were determined. AD was diagnosed by the Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria for probable AD and aMCI by the Petersen criteria.


RESULTS
We recruited 203 Chinese older men (48 aMCI, 66 AD and 89 with normal cognition). Mean serum BT, but not TT, levels were significantly lower in the aMCI (mean BT +/- SEM 1.06 +/- 0.10 nmol/l) and AD (0.99 +/- 0.08 nmol/l) groups than in the normal controls (1.82 +/- 0.12 nmol/l) (P < 0.001, one-way anova) with no significant difference between the aMCI and AD groups. After adjustment for education, age and apolipoprotein E (apoE) genotype, logistic regression analyses showed that the serum BT level [adjusted odds ratio (OR) = 0.52, 95% confidence interval (CI) 0.32-0.85] was an independent protective factor for aMCI. For the combined outcome of aMCI and AD, the serum BT level was an independent protective factor but age and apoE epsilon4 were independent risk factors. There was no interaction between BT and age.


CONCLUSIONS
In older men, serum BT, but not TT, levels were associated with a lower risk of aMCI and AD.
Chu
Leung-Wing
LW
Division of Geriatric Medicine, Department of Medicine, Queen Mary Hospital, Faculty of Medicine, The University of Hong Kong, Hong Kong SAR. lwchu@hkucc.hku.hk
Tam
Sidney
S
Lee
Peter W H
PW
Wong
Rachel L C
RL
Yik
Ping-Yiu
PY
Tsui
Wilson
W
Song
Youqiang
Y
Cheung
Bernard M Y
BM
Morley
John E
JE
Lam
Karen S L
KS
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood*; D001682:Biological Availability; D003071:Cognition / Q000502:physiology*; D003072:Cognition Disorders / Q000097:blood*; D003430:Cross-Sectional Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D013739:Testosterone / Q000097:blood*
D013739:Testosterone