Browsing by Author "Zheng, Mengjie"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Antihypertensive Medication and Dementia Risk in Older Adult African Americans with Hypertension: A Prospective Cohort Study
    (Springer, 2018-04) Murray, Michael D.; Hendrie, Hugh C.; Lane, Kathleen A.; Zheng, Mengjie; Ambuehl, Roberta; Li, Shanshan; Unverzagt, Frederick W.; Callahan, Christopher M.; Gao, Sujuan; Psychiatry, School of Medicine
    BACKGROUND: African Americans are especially at risk of hypertension and dementia. Antihypertensive medications reduce the risk of cardiovascular events, but may also reduce the risk of dementia. OBJECTIVE: To assess the longitudinal effects of antihypertensive medications and blood pressure on the onset of incident dementia in a cohort of African Americans. DESIGN: Prospective cohort. PARTICIPANTS: 1236 community-dwelling patients from an inner-city public health care system, aged 65 years and older, with a history of hypertension but no history of dementia, and who had at least three primary care visits and a prescription filled for any medication. MAIN MEASURES: Blood pressure was the average of three seated measurements. Dementia was diagnosed using a two-stage design, with a screening evaluation every 2 to 3 years followed by a comprehensive in-home clinical evaluation for those with a positive screen. Laboratory, inpatient and outpatient encounter data, coded diagnoses and procedures, and medication records were derived from a health information exchange. KEY RESULTS: Of the 1236 hypertensive participants without dementia at baseline, 114 (9%) developed incident dementia during follow-up. Individuals prescribed any antihypertensive medication (n = 816) were found to have a significantly reduced risk of dementia (HR = 0.57, 95% CI 0.37-0.88, p = 0.0114) compared to untreated hypertensive participants (n = 420). When this analysis was repeated including a variable indicating suboptimally treated blood pressure (> 140 mmHg systolic or >90 mmHg diastolic), the effect of antihypertensive medication was no longer statistically significant (HR = 0.65, 95% CI 0.32-1.30, p = 0.2217). CONCLUSIONS: Control of blood pressure in older adult African American patients with hypertension is a key intervention for preventing dementia, with similar benefits from most of the commonly available antihypertensive medications.
  • Thumbnail Image
    Item
    Changes of glucose levels precede dementia in African Americans with diabetes but not in Caucasians
    (Elsevier, 2018-12) Hendrie, Hugh C.; Zheng, Mengjie; Lane, Kathleen A.; Ambuehl, Roberta; Purnell, Christianna; Li, Shanshan; Unverzagt, Frederick W.; Murray, Michael D.; Balasubramanyam, Ashok; Callahan, Chris M.; Gao, Sujuan; Psychiatry, School of Medicine
    INTRODUCTION Changes in glucose levels may represent a powerful metabolic indicator for dementia in African Americans with diabetes. It is unclear whether these changes also occur in Caucasians. METHODS A secondary data analysis using electronic medical records from 5228 African Americans and Caucasians 65 years and older. Mixed effects models with repeated serum glucose measurements were used to compare changes in glucose levels between African Americans and Caucasian patients with and without incident dementia. RESULTS African Americans and Caucasians with diabetes had significantly different changes in glucose levels by dementia status (p<0.0001). African Americans experienced a significant decline in glucose levels before the dementia diagnosis (estimated glucose decline 1.3421 mg/dL per year, p<0.0001) than those who did not develop dementia. Caucasians with and without dementia showed stable glucose levels over time (p=0.3071). DISCUSSION Significant changes in glucose levels precede dementia in African American patients with diabetes but not in Caucasians.
  • Thumbnail Image
    Item
    Glucose level decline precedes dementia in elderly African Americans with diabetes
    (Elsevier, 2017-02) Hendrie, Hugh C.; Zheng, Mengjie; Li, Wei; Lane, Kathleen; Ambuehl, Roberta; Purnell, Christianna; Unverzagt, Frederick W.; Torke, Alexia; Balasubramanyam, Ashok; Callahan, Chris M.; Gao, Sujuan; Psychiatry, School of Medicine
    INTRODUCTION: High blood glucose levels may be responsible for the increased risk for dementia in diabetic patients. METHODS: A secondary data analysis merging electronic medical records (EMRs) with data collected from the Indianapolis-Ibadan Dementia project (IIDP). Of the enrolled 4105 African Americans, 3778 were identified in the EMR. Study endpoints were dementia, mild cognitive impairment (MCI), or normal cognition. Repeated serum glucose measurements were used as the outcome variables. RESULTS: Diabetic participants who developed incident dementia had a significant decrease in serum glucose levels in the years preceding the diagnosis compared to the participants with normal cognition (P = .0002). They also had significantly higher glucose levels up to 9 years before the dementia diagnosis (P = .0367). DISCUSSION: High glucose levels followed by a decline occurring years before diagnosis in African American participants with diabetes may represent a powerful presymptomatic metabolic indicator of dementia.
  • Thumbnail Image
    Item
    Joint modeling of longitudinal and survival outcomes using generalized estimating equations
    (2018-05-07) Zheng, Mengjie; Gao, Sujuan; Xu, Huiping; Zhang, Jianjun; Zhang, Ying
    Joint models for longitudinal and time-to-event data has been introduced to study the association between repeatedly measured exposures and the risk of an event. The use of joint models allows a survival outcome to depend on some characteristic functions from the longitudinal measures. Current estimation methods include a two-stage approach, Bayesian and maximum likelihood estimation (MLEs) methods. The twostage method is computationally straightforward but often yields biased estimates. Bayesian and MLE methods rely on the joint likelihood of longitudinal and survival outcomes and can be computationally intensive. In this work, we propose a joint generalized estimating equation framework using an inverse intensity weighting approach for parameter estimation from joint models. The proposed method can be used to longitudinal outcomes from the exponential family of distributions and is computationally e cient. The performance of the proposed method is evaluated in simulation studies. The proposed method is used in an aging cohort to determine the relationship between longitudinal biomarkers and the risk of coronary artery disease.