Chih-Ta Tai

Prevalence and subtypes of dementia in southern Taiwan: Impact of age, sex, education, and urbanization

To determine the prevalence and subtypes of dementia in southern Taiwan, a two-phase study consisting of a phase I screening survey using the Mini-Mental Status Examination (MMSE) and a phase II diagnostic examination using the CERAD neuropsychological battery and the neurobehavioral examination was conducted. According to the household records, stratified random sampling by the degree of urbanization of the community was used, and 2915 inhabitants aged 65 and over participated in this study. The ICD-10NA criteria for dementia, NINCDS-ADRDA guidelines for Alzheimers disease (AD), and NINDS-AIREN criteria for vascular dementia (VaD) were employed. Three hundred and ninety-eight persons who had MMSE scores below the cutoff values were recruited into the phase II study, of whom 108 had dementia. The prevalence rate (PR) of dementia was 3.7%, increasing from 1.3% in people 65-69 years old to 16.5% in people 85 years old and older. The age-standardized PR (ASPR) was 4.0%. AD (58 cases, 53.7%, PR=2.0%, ASPR=2.3%) was the most common cause of dementia, followed by VaD (25 cases, 23.1%, PR=0.9%, ASPR=0.9%), and mixed dementia (eight cases, 7.4%). After adjusting for age, sex and education using logistic regression analysis, aging was a significant risk factor for AD, VaD and total dementia. Female sex and illiteracy were significant risk factors for AD only. We concluded that the prevalence of dementia in Taiwan is lower than in the developed countries, which could be due to a relatively young elderly population and a high mortality from dementia in Taiwan. AD is the leading cause of dementia in Taiwan. Considering the high stroke prevalence, the relatively lower prevalence of VaD in Taiwan deserves further investigation.

Apolipoprotein E Polymorphism in Ischemic Cerebrovascular Diseases and Vascular Dementia Patients in Taiwan

This study aims to clarify the association between apolipoprotein E gene (ApoE) polymorphism, ischemic cerebrovascular diseases (ICVD) and vascular dementia (VaD) in Taiwan Chinese. 277 patients with ICVD, 49 patients with probable VaD and 112 controls were recruited for this study. Distributions of ApoE Ε4 carriers and allele frequencies were 28.5 and 14.5% for patients with ICVD, 20.4 and 10.2% for patients with VaD, whereas these values were 22.9 and 11.6% for controls. Distributions of ApoE Ε2 carriers and allele frequencies were 10.1 and 5.2% for ICVD patients, 6.1 and 3.1% for VaD patients, but 12.5 and 8.0% for controls. There were no differences between ICVD patients and controls, or VaD patients and controls in their Ε4 carriers. Those patients aged 65 and under, carrying the Ε2 allele, had a lower risk of developing ICVD and VaD than did their counterparts. These findings suggest that ApoE Ε4 plays no significant role in the development of ICVD and VaD, but that ApoE Ε2 has a protective effect with regard to the development of ICVD and VaD for Taiwan Chinese below the age of 65.

Chromosome 9p21 Genetic Variants Are Associated With Myocardial Infarction But Not With Ischemic Stroke in a Taiwanese Population

Background Genetic variants on chromosome 9p21 confer a robust risk for coronary artery disease but inconsistent risk for stroke. This study investigated whether such genetic variants exert differential risks on myocardial infarction (MI) and ischemic stroke in a Taiwanese population. Methods The study recruited 425 MI patients, 687 patients with ischemic stroke, and 1377 healthy controls. Four key single nucleotide polymorphisms (SNPs) on chromosome 9p21 were genotyped. Results Multivariate permutation analyses demonstrated that the risk T allele of rs1333040 and G allele of rs2383207 were associated with MI (P = 0.045 and 0.002, respectively). Subjects with the rs2383207 GG genotype had a 1.85-fold (P = 0.021) risk for MI when compared with the subjects with the AA genotype. Further analysis showed that significant results only exist in the young MI group (<65 years) but not in the old MI group (≥65 years). These SNPs were not statistically significant for stroke (adjusted P ranged from 0.097 to 0.540). Haplotype analysis showed global P values of 0.032 for MI and 0.290 for stroke. Conclusions Genetic variations in the 9p21 region are associated with MI but not with stroke in a Taiwanese population. Early-onset MI was more likely to carry the risk genotypes of 9p21 SNPs.

A longitudinal study of central and peripheral nerve conduction in hypothyroid rats

In order to detect the dysfunction of central and peripheral nervous systems among rats with varied duration of hypothyroidism and to elucidate the pattern of recovery after thyroxine replacement, a series of BAEP and PNCS (Peripheral Nerve Conduction Study) were conducted and compared with age-matched controls. BAEP and PNCS were performed in three groups of hypothyroid animals 1, 3 and 5 months after thyroidectomy, respectively. Following initial electrophysiological assessment, thyroxine replacement was administered to each group of hypothyroid rats, and BAEP and PNCS were performed at two month intervals, up to two successive normal studies, or six months after the initiation of therapy, whichever came first. For BAEP, prolonged I-V interpeak latency was the most consistent abnormal finding in all groups of hypothyroid rats, and longer hypothyroid states correlated well with more severe central conduction disorder. Nevertheless, these abnormalities usually returned to normal after thyroxine replacement if the duration of hypothyroidism was less than 5 months. Regarding PNCS, all groups of thyroidectomized rats showed normal conduction before and after thyroxine therapy. The present study indicates that, in rats: (1) the peripheral nervous system seems to be more resistant to hypothyroidism than the central nervous system, or (2) the pathogenesis of central and peripheral nerve dysfunction in hypothyroid rats may occur through different mechanisms.

Association of apolipoprotein E polymorphism with ischemic stroke subtypes in Taiwan.

The aim of this study was to clarify whether the apolipoprotein E gene (APOE) is related to ischemic stroke subtypes in Taiwans Chinese population. Using the classification of Cerebrovascular Diseases III, 143 patients with lacunar infarction, 114 patients with atherothrombotic infarction, and 112 healthy controls were enrolled. APOE genotype was determined using polymerase chain reaction. Regarding the distribution of APOE genotypes, the frequency of ɛ3/ɛ4 genotypes in lacunar patients was significantly different from that in control subjects, by logistic regression, using ɛ3/ɛ3 as a reference group. There was no significant difference between atherothrombotic patients and the control group in the distribution of APOE genotypes or alleles. The present finding suggests that there is a probable association between ɛ3/ɛ4 genotype and lacunar infarcts, but not atherothrombotic infarcts. This indicates that genetic factors may play a role, at least partially, in lacunar infarction in Taiwans Chinese population.

Hypothyroid Myopathy-Pathological and Ultrastructural Study

Seventeen patients with hypothyroid myopathy were studied before and after thyroxine (T4) treatment. The severity of clinical myopathy was assessed with the aid of a modified rating scale. Laboratory findings including thyroid function, serum creatine kinase (CK), and electromyography were assessed at regular time intervals until a final muscle biopsy was performed. The average period of follow-up was 1.8 years. The authors emphasize: 1) in skeletal muscle pathology of hypothyroidism, the fiber atrophy and increased central nuclear counts are evidence of clinical myopathy during thyroxine treatment; 2) in ultrastructural pathology, the abnormal glycogen accumulation accounts largely for clinical severity and its ongoing resolution is parallel to steady amelioration following T4 therapy, while mitochondrial abnormalities are insignificant in clinical correlation and probably become permanent in some cases with prolonged hypothyroidism; and 3) serial needle biopsies of skeletal muscle are impractical for long-term study of hypothyroid myopathy, but they may be reserved for those patients with a sustained myopathic complaints on T4 therapy.

Cut-Off Values of Blessed Dementia Rating Scale and Its Clinical Application in Elderly Taiwanese

Although the Blessed Dementia Rating Scale (BDRS), a clinical screening instrument, has been applied extensively, no suitable cut‐off values and clinical application have been proposed, particularly in mild cognitive impairment (MCI), the precursor of dementia. The BDRS, Mini Mental State Examination (MMSE), and Clinical Dementia Rating Scale (CDR) were administrated in people aged 65 years and above, who were enrolled from southern Taiwan with multistep stratified random sampling and followed‐up for 2 years. All subjects (total number = 3,027), with new onset of MCI (defined as CDR = 0.5) in the first year and dementia (defined as CDR ≥ 1) in the second and third years were subjected to statistical analysis. In distinguishing normal from MCI, except in the literate group aged 65‐74 years, MMSE was superior to BDRS, with cut‐off values of 1 in both literate groups aged 65‐74 years and ≥ 75 years, and 1.5 and 2 in less educated groups aged 65‐74 and ≥ 75 years, respectively. In distinguishing MCI from dementia, BDRS had cut‐off values of 2.5 in both literate groups aged 65‐74 and ≥ 75 years, and 2.5 and 3 in less educated groups aged 65‐74 and ≥ 75 years, respectively. These values were better than those for MMSE in all groups. BDRS might be considered as a better tool than MMSE to screen for MCI and dementia in the increasing proportion of literate elderly aged 65‐74 years in the aging population.

A study of central and peripheral nerve conduction in patients with primary hypothyroidism: the effects of thyroxine replacement.

Somato-Sensory Evoked Potential (SSEP) and Peripheral Nerve Conduction (PNC) studies were performed in twenty patients with primary hypothyroidism to elucidate the changes of central and peripheral nervous systems in hypothyroid state and the effects of thyroxine replacement. Before thyroxine replacement therapy, eleven patients had significantly delayed SSEP (prolonged latencies of N9, N13, or N20), and only three patients had prolonged central conduction time (between N13 and N20). PNC abnormalities with decreased conduction velocity and diminished amplitudes were found in fourteen patients. After thyroxine treatment, both SSEP and PNC studies demonstrated significant improvement and paralleled the clinical neurological amelioration. The central and peripheral conduction velocities returned to normal limits, while the abnormality in amplitude still persisted. There were also discrepancies between SSEP and PNC studies in both the abnormality pattern and the recovery potential. Our observations may suggest: firstly, both the SSEP and PNC studies may be useful, alternative tools in monitoring the neurological disorders in hypothyroidism; and secondly, the pathogenesis of central and peripheral nervous dysfunction in hypothyroidism may be via different mechanisms.