Tardive Dyskinesia (TD) is a serious, nonrhythmic and iatrogenic movement disorder, and is a common comorbidity in patients with schizophrenia (SZ). The main goal of this study was to investigate the prevalence, clinical correlates, and risk factors of TD in Chinese patients with chronic SZ, which has not been fully studied. This study adopted a cross-sectional design. A total of 901 Chinese inpatients with SZ were recruited between 2008 and 2011. We used the Abnormal Involuntary Movement Scale (AIMS) to measure the severity of TD, and the Positive and Negative Syndrome Scale (PANSS) was used to measure the psychopathological symptoms of SZ. Blood samples were also collected for routine blood tests, including the levels of triglyceride (TG), cholesterol (CHO), HDL-cholesterol (HDL-CHO), LDL-cholesterol (LDL-CHO), Apolipoprotein A1 (ApoA1), and Apolipoprotein B (ApoB). Overall, 36% of patients with SZ had TD. Compared with the non-TD patients, the TD patients were more likely to be men, had older age, lower education level, higher smoking rate, higher hospitalization frequency, and longer duration of illness (DOI). Further, compared with the non-TD patients, the TD patients had higher PANSS total, PANSS negative subscale, and cognitive subscale scores, but had lower depressive subscale scores and lower mean levels of metabolic biomarkers, including TG, CHO, HDL-CHO, LDL-CHO, ApoA1 and ApoB. Moreover, binary regression analysis showed that antipsychotic type, BMI, gender, age, HDL-CHO, and ApoB were associated with TD. Our findings indicate that TD is a common movement disorder in patients with chronic SZ, with certain demographic and clinical variables being risk factors for the development of TD.
https://pubmed.ncbi.nlm.nih.gov/34638091/
Commentary: Why Calculating Prevalence Matters in This Tardive Dyskinesia Study
Estimating the prevalence of Tardive Dyskinesia (TD) in this cohort of 901 Chinese inpatients with chronic schizophrenia is not merely a descriptive exercise—it is the essential first step that gives meaning to all subsequent analyses of clinical correlates and risk factors. Without a reliable prevalence estimate, clinicians cannot gauge the burden of TD, researchers cannot contextualize their findings, and public health planners cannot allocate resources.
Here is why prevalence is indispensable in this study:
1. Prevalence quantifies the clinical and public health burden
Finding that 36% of patients have TD is striking. It tells clinicians that among every three chronic schizophrenia inpatients, more than one suffers from this iatrogenic movement disorder. This number immediately signals that TD is not a rare complication but a common comorbidity. Without the prevalence figure, statements like “TD is common” remain subjective. With 36%, the message is clear: TD is a major and frequent problem in this population, warranting routine screening and prevention strategies.
2. Prevalence enables comparison across populations and time
The 36% prevalence can be compared to previous studies (e.g., Western samples, different generations of antipsychotics) and to future investigations. This allows researchers to ask: Is TD more common in Chinese patients? Has the switch to atypical antipsychotics reduced prevalence compared to older reports (which often ranged 20–50%)? Such comparisons are impossible without a standardized prevalence estimate.
3. Prevalence defines the baseline risk for risk factor analysis
The binary regression analysis identifies predictors of TD (antipsychotic type, BMI, gender, age, HDL‑CHO, ApoB). However, the strength and clinical relevance of those associations depend on knowing how many patients are at risk. If prevalence were only 1%, even a strong odds ratio might have little public health impact. With 36%, even modest risk factors affect a large segment of the population. Prevalence also determines sample size adequacy: N=901 was clearly sufficient to detect differences because the event rate (TD) was substantial.
to cite:
Uludag, K., Wang, D. M., Goodman, C., Chen, D. C., Wang, L., & Zhang, X. (2021). Prevalence, clinical correlates and risk factors associated with Tardive Dyskinesia in Chinese patients with schizophrenia. Asian journal of psychiatry, 66, 102877. https://doi.org/10.1016/j.ajp.2021.102877
