Depression and Serum Lipids and Lipoprotein in Chinese Nonagenarians and Centenarians

To the Editor: Abnormality of serum lipids and lipoproteins (including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C)) has been viewed as a common and potentially modifiable risk factor for depression.1, 2 Not all previous studies reached the same conclusion about association between serum lipids and lipoproteins and depression; a few studies showed that such association was not significant.3-5 Common to each of these studies was the relatively young age of the participants, although no data were for available for the association between depression and clinically abnormal levels of serum lipids and lipoproteins and the association between depression and the lowest serum cholesterol values. We report here the results of a cross-sectional study of age-related diseases conducted in 870 long-lived subjects (≥90). Depressive symptoms were measured using a brief 23-item Geriatric Depression Scale—Chinese Edition (GDS-CD). The GDS-CD is scored on a scale of 0 to 23; a score between 10 and 15 indicates minor depression, and higher than 15 indicates major depression. Blood samples were collected after an overnight fast (≥8 hours) for measurement of serum lipids and lipoproteins. Lipids and lipoproteins, including serum TC, TG, HDL-C, and LDL-C, were determined using standard laboratory techniques (performed by a technician in the biochemistry laboratory of Sichuan University). Abnormal levels of serum lipids and lipoproteins were defined according to the criteria provided by the Chinese Medical Association 2004-Edition (normal criteria: TC<5.18 mmol/L, TG<1.7 mmol/L, LDL<3.37 mmol/L, and HDL> 1.04 mmol/L). Of the 678 volunteers, mean age was 93.4±3.2 (range 90–108), and 455 (67.8%) were women, including 76 centenarians. Ninety percent of subjects lived in the countryside. The mean depression score for the sample was 8.3±2.2 (range 0–23). In the oldest-old population, the total prevalence rate of depression (GDS-CD score ≥10) was 33.3%. The prevalence rate of high serum TG, TC, LDL-C, and HDL-C were 14.01%, 11.50%, 5.31%, and 5.98%, respectively. There were no significantly different levels of serum lipids and lipoproteins (including TG, TC, HDL-C, and LDL-C) between subjects with and without depression (TG: mean difference (MD)=0.01, P=.84; TC: MD=0.01, P=.91; LDL-C: MD=0.01, P=.84; HDL-C: MD=−0.01, P=.98; and MD=−0.03, P=.44). Pearson correlation showed that depression scores were not correlated with levels of serum lipids and lipoproteins (TG: correlation coefficient (R)=0.04, P=.34; TC: R=0.02, P=.56; LDL-C: R=−0.01, P=.98; and HDL-C: R=0.06, P=.14). Depression scores in subjects with clinically abnormal levels of serum lipids and lipoproteins were not significantly different from those in subjects with clinically normal levels (TG: MD=0.31, 95% confidence interval (CI)=−0.51–1.13; TC: MD=−0.08, 95% CI=−0.79–0.65; LDL-C: MD=0.33, 95% CI=−0.71–1.36; HDL-C: MD=−0.87, 95% CI=−1.77–0.04), and there was no significant difference in prevalence rates of depression between subjects with and without clinically normal levels of serum lipids and lipoproteins (TG: chi-square (χ2)=0.261, P=.61; TC: χ2=0.098, P=.75; LDL-C: χ2=0.53, P=.47; HDL-C: χ2=0.213, P=.64). Odds ratios (unadjusted and adjusted) of depression according to clinically abnormal levels of serum lipids and lipoproteins were not statistically significant (Table 1). After adjustment for age, body mass index, smoking habits, tea habits, cognitive function, alcohol consumption, and fasting plasma glucose, the odds ratio comparing the lowest quartile with the highest of TC was 0.960 (95% CI=0.49–1.31). All of these showed that, among Chinese nonagenarians and centenarians, clinically abnormal levels of serum lipids and lipoproteins were not directly correlated with depression and the lowest serum cholesterol values were not a risk for depression. Although in recent decades, association between depression and lipids and lipoproteins have been generally studied, the cross-sectional observations are still important. First, this study extended the findings of previous studies, because the subjects in the study were all aged 90 and older. To the best of the authors' knowledge, no other researchers have specifically evaluated the association between depression and serum lipids and lipoproteins in the oldest old (≥85). This study gave the relevant information in community-dwelling oldest-old persons. Second, the association between clinically abnormal levels of serum lipids and lipoproteins and depression in elderly people was still indefinite. This study provided evidence of no causal association between clinically abnormal levels of serum lipids and lipoproteins and depression in community-dwelling oldest-old persons. Third, abnormally high and low serum cholesterol are generally viewed as risks for depression. The present study found that, in nonagenarians and centenarians, levels of serum cholesterol (abnormally high and lower) were independent of depression. This work was supported by Discipline Construction Foundation of Sichuan University. The authors thank the staff of the Department of Geriatric Medicine, West China Hospital and Dujiangyan Hospital, and all participants (as well as their legal proxies) for their great contribution. Mr. Rebbo is also acknowledged for language assistance. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this letter. Author Contributions: Yue Ji-Rong and Dong Bi-Rong had equal contribution to this study and were the main designers and participants. Wu Hong-Mei, Huang Chang-Quan, and Zhang Yan-Ling were participants and assistants. Sponsor's Role: None.