Zhenxin Zhang

Motor neuron disease on Guam: Geographic and familial occurrence, 1956-85

We investigated the geographic and familial occurrence of motor neuron disease (MND) on Guam, and then considered etiologic hypotheses related to cycad use and metal intoxication. The research was based on 303 Chamorros from Guam and 3 Chamorros from other Mariana Islands, all with MND onset on Guam during 1956–85. Inarajan and Umatac, two southern districts, each had, for both sexes combined, an average incidence rate significantly higher than the corresponding overall rate for Guam. Also, for each sex, geographic patterns of incidence were significantly related to 1)socioeconomic level (men only), 2)cycasin concentrations in cycad flour samples (men and women), 3)iron concentrations in water samples (men and women), 4)silicon concentrations in water samples (men only), and 5)cobalt and nickel concentrations in soil samples (men and women). The MND risk in susceptible sibships was about 7–28 times greater than that in the general population. The cycad hypothesis conforms somewhat better than the metal intoxication hypothesis with the data presented.

Prevalence of Parkinson's disease and related disorders in the elderly population of greater Beijing, China.

A lower prevalence of Parkinsons disease (PD) has been reported for Chinese populations, but it is unclear whether this observation reflects a lower disease risk or is an artifact of case finding. We ascertained the prevalence of PD in elderly residents of an area that was a composite of 27 urban and rural communities of Greater Beijing, China. A team of university neurologists went door‐to‐door throughout the study area, examining 5,743 residents (at age 55 years or older) and made preliminary determinations of which residents had PD or other types of parkinsonism. Final determinations were made after follow‐up and reevaluation of those persons who were either deemed to have parkinsonism or were suspected of having the condition (n = 144; median follow‐up = 40 months). Based on stringent diagnostic criteria, 110 persons were identified to have parkinsonism, of whom 64 (58%) had PD. The prevalence of PD increased with advancing age and was about 1% overall and for each gender. In rural communities, 22 persons had PD, but 20 persons (91%) were first diagnosed for this condition by the study neurologists. The prevalence figures obtained in this study are similar to some of the highest prevalence figures reported in the West.

Progression of Mild Cognitive Impairment to Alzheimers or Vascular Dementia Versus Normative Aging Among Elderly Chinese

To compare differences in evolutionary progressions from Mild Cognitive Impairment (MCI) to dementia of Alzheimers type (DAT) or to vascular dementia (VaD) versus normal aging, subjects identified as MCI or as cognitively normal (CN) during standard cognitive evaluations among a large epidemiological study designed to determine prevalence and incidence of dementia and its major subtypes in Beijing, China were re-examined after an interval of approximately 3 years, repeating the same investigation protocol as at baseline. MCI subjects meeting criteria for dementia and the two major subtypes, DAT and VaD were identified at follow-up evaluation. Annual conversion rates for combined dementias and for major subtypes of DAT and VaD, from MCI, were compared with conversion rates among CN subjects. Relative risks for conversion from MCI to major subtypes of dementia were also compared with CN subjects by Cox regression models. 175 MCI and 400 CN subjects were identified at baseline. Among 121 MCI subjects available at follow-up, 51 were diagnosed with dementia (29 with DAT, 18 with VaD and 4 with other dementias), compared with 14(10 DAT, 3 VaD and 1 other type dementia) diagnosed as dementia among 281 CN subjects available at follow-up. Annual conversion rates calculated from MCI to all dementias, compared with conversion rates from CNs, were 14.1% versus 1.6%. Specifically for DAT, annual conversion rates were 8.0% versus 1.1% and for VaD were 5.0% versus 0.3%. Relative risks for developing all dementias, DAT and VaD among MCI subjects were 9, 6 and 5 times greater than among CN subjects. Conversion rates among MCI subjects to dementia, and major subtypes, for elderly Chinese residents of Beijing were comparable with results reported among similar studies worldwide. Risks of developing dementia, and major subtypes, among MCI subjects in Beijing were significantly higher than among normal subjects. Identification of MCI among elderly populations provides the possibilities for dementia prevention and treatment within prodromal stages.

Incidence of dementia and subtypes: A cohort study in four regions in China.

There is a dearth of literature on the incidence of dementia in China.

Motor neuron disease on Guam: Temporal occurrence, 1941-85

Using a case registry, we investigated the temporal occurrence of motor neuron disease (MND) on Guam. MND with onset during 1941–85 was documented in 434 Chamorros and 9 non‐Chamorro migrants who had lived on Guam before onset. Increased median age at onset and decreased age‐adjusted incidence rates (since the early 1960s) were observed for Chamorros of both sexes. Our evidence about MND on Guam is consistent with: 1) The latent period duration has varied from years to decades; 2) With time, the exposure period or latent period, or both, have lengthened; 3) The high risk of acquiring the condition has been reduced since, at least, the early 1950s, and the most recent years of meaningful risk were the early to middle 1960s; 4) The critical age for acquiring the condition is in adolescence and adulthood; 5) Change of environment from Guam to overseas during childhood resulted in decreased risk of acquiring the condition.

Validity of auditory verbal learning test in diagnosis of Alzheimer's disease.

OBJECTIVE To assess the validity of World Health Organization-University of California-Los Angeles Auditory Verbal Learning Test (WHO-UCLA AVLT) in the diagnosis of Alzheimers disease (AD). METHODS Using WHO-UCLA AVLT, we assessed 183 AD patients (AD group),1283 subjects with normal cognitive status (normal control group), and 134 individuals suffered from other diseases easy to be confused with AD (confused control group). RESULTS The AVLT score was 40.9∓0.3 in normal control group, 30.7∓0.9 in confused control group, 16.6∓1.0 in mild AD group, and 10.2∓1.2 in moderate AD group after adjustment for educational level, age, sex, and rural/urban residence (all P<0.05). With the 5th percentage of the overall score as the cutoff point, this tool showed a sensitivity of 86.3% and a specificity of 93.3%. CONCLUSION WHO-UCLA CVLT is highly sensitive and specific in the diagnosis of AD.

Mortality of Dementia and Its Major Subtypes in Urban and Rural Communities of Beijing

OBJECTIVE To identify the mortality and epidemiological pattern of dementia and its various major subtypes among urban and rural senior residents in Beijing. METHODS Based on Beijings dementia prevalence survey among residents aged 55 years and above in 1997, respondents were selected by stratified multiple-stage cluster sampling and 12 urban communities and 17 rural village communities were randomly sampled then follow-up in 2001. COX regression was used to analyze relative risks controlling confounding factors on deaths of dementia cases. RESULTS The mortality of dement patients in the 55-64 age-group was 0.82/100 person-year. The age-standardized mortality of dement cases was 0.90/100 person-year. The mortality in the 65 and above age-group was 1.44/100 person-year, and the age-standardized mortality was 1.56/100 person-year. Among AD cases, the above two mortalities were 0.35/100 and 0.42/100 person-year respectively, and among VaD cases, 0.34/100 and 0.36/100 person-year respectively. For both AD and VaD cases, their mortality increased with age. Region, gender and age were more significant to survival of AD cases. CONCLUSION One major subtype of dementia, AD, among elderly urban and rural residents in Beijing, has a different mortality and epidemiological pattern from VaD.

Validation of an Alzheimerâs Disease Assessment Battery in Asian ParticipantsWith Mild to Moderate Alzheimerâs Disease

There is a lack of validated tools for assessing Alzheimers disease (AD) across Asia. This study evaluates the psychometric properties of the Alzheimers Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), Disability Assessment for Dementia (DAD), and Neuropsychological Test Battery (NTB) in Asian participants. Participants with mild to moderate AD (n=251) and healthy controls (n=51) from Mainland China, Taiwan, Singapore, Hong Kong, and South Korea completed selected instruments at several time points. Test-retest reliability was better than 0.70 for all tests. AD participants performed significantly more poorly than controls on every score. Within the AD group, greater disease severity corresponded to significantly poorer performance. The AD group test performance worsened over time and there was a trend for worse performance in AD compared to healthy controls over time. The ADAS-Cog, DAD, and NTB are reliable, valid, and responsive measures in this population and could be used for clinical trials across Asian countries/regions.

[Validity of complex figure test in differentiation of Alzheimer's disease from non-dementia].

OBJECTIVE To assess the validity of Complex Figure Test(CFT)in differentiating Alzheimers disease(AD)from non-dementia. METHODS Using CFT,we tested 183 AD patients(AD group),1283 cognitively intact individuals(normal control group),and 134 individuals suffered from other diseases that could be easily confused with dementia(confused control group). RESULTS The CFT score was 38.7±0.2 in the normal control group,35.3±0.8 in confused control group,23.7±0.8 in mild AD group,and 13.2±1.1 in moderate AD group after adjusted for educational level,age,and sex(all P<0.05).With the 5(th) percentage of the overall score as cutoff point,this tool showed a sensitivity of 73.8% and a specificity of 93.8% in differentiating AD from non-dementia. CONCLUSION CFT is a sensitive and specific tool in the differentiation of AD from non-dementia.

Early Cognitive Predictors of Vascular Dementia: A Population-based Longitudinal Study in Chinese Elderly

Background and Objectve: Mild cognitive impairment (MCI) as pre-dementia syndrome has not been thouroughly studied in underdeveloped regions with cultural and social-economic backgrounds different from Western countries. This study was designed to characterize cognitive profiles of MCI prodromal for vascular dementia (VaD) among an elderly Chinese population. Methods: Subjects identified with MCI in a large epidemiological study of dementia and major subtypes in Beijing, China, were re-examined three years later, by repeating the baseline psychometric protocol. Baseline versus follow-up psychometric performance was compared among two outcome groups: 1) MCI converting to VaD (MCI-VaD) and 2) MCI-Non-converters. Results: 121 of 175 subjects identified as MCI at baseline were available for follow-up, with 18 diagnosed VaD, 70 didn’t convert to any dementias. At baseline, MCI-VaD displayed extensive impairments in attention, naming and verbal fluency. At the time of dementia diagnosed, multiple cognitive domains declined significantly. Conclusions: The present study provided additional evidence for the existence of prodromal VaD in an elderly Chinese population. The distinctive cognitive patterns of prodromal VaD allowed for an early intervention and improved control of vascular risk factors, which were less well controlled for than in developed countries.