Prevalence of Chronic Diseases and Multimorbidity Among Urban Community-Dwelling Elderly Individuals in Northeastern China


 Background: To evaluate the prevalence of chronic diseases and multimorbidity in the elderly population in an urban community in northeastern China.Methods: A quantitative, descriptive, cross-sectional study was conducted among an elderly population (≥60 years) in the community of Changchun, China, in 2018. The following were used: a sociodemographic questionnaire, anthropometric data, and laboratory examinations. A total of 2171 elderly residents (1328 male) were finally enrolled. Data on 5 chronic diseases—hypertension, diabetes, dyslipidemia, coronary heart disease (CHD) and chronic kidney disease (CKD) —were collected by interviews and physical check-ups and confirmed by physicians.Results: The age-adjusted prevalences of the five chronic diseases (hypertension, diabetes, dyslipidemia, CHD and CKD) were the following: 67.60%, 63.30%, 61.50%, 51.00% and 8.98%, respectively, in men and 64.10%, 59.70%, 71.10%, 44.80% and 19.70%, respectively, in women. A total of 77.0% of hypertensive subjects were aware of their hypertension status, and 61.0% had their blood pressure controlled. The awareness rate of diabetes was 82.1%, and the controlled rate was 68.4%. A total of 75.4% of the population had two or more chronic conditions, which is called multimorbidity. The elderly individuals had the highest frequency of multiple chronic conditions.Conclusion: The prevalence of chronic diseases in the elderly was high, and a significant proportion was affected by multimorbidity in urban China. Chronic diseases are important diseases threatening the health of the elderly population.


Background
Today, the phenomenon of the increasing ageing population is a worldwide issue that will result in workforce shortages and increased medical expenditures, in addition to other negative consequences.
The percentage of the global population aged 60 and over was 11% by the end of 2011 1 . As the world's largest developing country, China is also facing severe aging problems, with the aging population currently accounting for 13% (177 million) according to the latest national census in 2010 2 . However, the elderly population is expected to increase to 25% by 2030 3 . China has undergone a swift health transition due to the rapid aging process. The spectrum of people's diseases is now dominated by chronic diseases, such as cardiovascular diseases, hypertension, diabetes and chronic kidney disease, especially in the aged, which are the leading causes of death in China, accounting for 86.6% of all deaths as well as 70% of disability-adjusted life-years lost in 2012 4 . They cause a tremendous burden, not only for the affected individuals but also for society as a whole.
A large-scale CNNHS survey on the prevalence of chronic conditions and chronic disease risk factors was conducted in China 5,6 . Nonetheless, the sample was the general population and lacked representation of Page 3/12 older adults. Although some studies on chronic diseases in elderly individuals have been conducted in China 3,5,7,8 , data from the northeast are relatively rare.
The concept of multimorbidity has attracted growing interest in recent years. It is recognized that this is of particular relevance to older adults. Patients suffer from more than one kind of chronic disease, de ned as multimorbidity 9 . To our knowledge, some epidemiologic studies on multimorbidity have been conducted in most countries. For example, almost two-thirds of people aged over 65 years have been affected by multimorbidity 10 ; the mean number of chronic conditions was found to be 17 among care home residents in one German study 11 . In China, there is also some data on multimorbidity 12,13 . However, information about elderly individuals in general is still greatly needed in northeastern China.
In the current study, we evaluated the prevalence of ve chronic diseases and the status of multimorbidity among the elderly population of an urban community in Changchun, which is located in northeastern China.

Study setting and data collection
This study used a cross-sectional design to observe the prevalence of the ve chronic diseases and the multimorbidity of the elderly population in Changchun city, which is the capital of Jilin Province in northeastern China. We used a multistage and strati ed random sampling method to select subjects aged ≥60 in Changchun City. The sample size was calculated based on a 31.7% prevalence (P) of chronic diseases 3 with a 3.0% uncertainty level (E) using the formula N = Z 2 PQ/E 2 (where Z = 1.96 with 95% con dence intervals). We estimated that a total of 924 subjects would be needed.
These subjects underwent interviews, physical examinations and related laboratory tests. A total of 2184 elderly people participated in this study, excluding those with incomplete data, and 2171 subjects aged 60-88 were nally enrolled.
Information was collected through face-to-face interviews with the respondents or with a household member for those who were disabled for reading or answering.
Anthropometric data included height, weight, waist circumference (WC) and blood pressure(BP). Standing height was recorded to the nearest 0.1 cm. Body weight was measured to the nearest 0.1 kg using an electronic scale. Body mass index (BMI) was calculated as weight (kg) divided by the square of height (m 2 ) 14 . Blood pressure was recorded three times at 1-minute intervals by a trained nurse using an upper arm electronic monitor (Omron). The mean values for each participant were then calculated 15 .

Disease De nition
In this study, chronic diseases included hypertension, diabetes, dyslipidemia, CHD and CKD. Self-reported chronic disease status was obtained by asking the question, "Have you been diagnosed by a physician with the following conditions?" Diabetes was de ned as FPG≥7.0 mmol/L, previous diagnosis by a physician or the use of insulin or oral hypoglycemic agents 16 .
Hypertension was de ned if the subjects had a mean systolic blood pressure (SBP)≥140 mmHg or a mean diastolic blood pressure (DBP)≥90 mmHg 15 , were already taking antihypertensive medication, or had any self-reported history of hypertension.
Coronary heart disease (CHD) was de ned as a positive response by self-report 8 .
An eGFR (glomerular ltration rate) less than 60 (min×1.73 m 2 ) or proteinuria was de ned as CKD 18 . eGFR was calculated according to the Modi cation of Diet in Renal Disease (MDRD) Study 19 . We de ned proteinuria as the presence of protein (>1+) in a spot urine dipstick analysis due to the lack of quantitative data 20 .
Statistical analysis Continuous variables were tested using the Kolmogorov-Smirnov test for normality, and nonnormal data are presented as medians and quartiles. The Mann-Whitney U test and Wilcoxon signed ranks test were used to assess differences between the two groups. Categorical variables are presented as frequencies (percentages) and were analyzed using the chi-squared test. The prevalence of chronic diseases was standardized by age (ASR) using direct standardization based on the population composition of the Sixth National Population Census of China (2010). For standardization, we divided the participants into four age groups (60-64 years, 65-69 years, 70-74 years and ≥75 years). Data were collected and analyzed using SPSS 20 (SPSS, Inc., Chicago, IL, USA). P values < 0.05 were considered statistically signi cant.

Results
1. Characteristics of urban elderly individuals aged over 60 years in Changchun in 2018 A total of 2171 community elderly residents (1328 male) were nally enrolled in the 2018 survey (as shown in Table 1). All participants were of Han origin. We divided the participants by sex. Men had signi cantly higher WC, DBP, Scr, and eGFR levels than women. However, women's TG and TC were signi cantly higher than those of men. The other variables were not signi cantly different between the two sexes.
2. Prevalence of the ve chronic diseases among the elderly in the community The crude and age-standardized prevalences of the chronic diseases are shown in Table 2. The prevalence of hypertension, diabetes and CHD was higher in men than in women. However, the prevalence of dyslipidemia and CKD was lower in men than in women. More than half of the elderly had hypertension, diabetes and dyslipidemia.
In the available data, we analyzed the awareness and treatment rates of hypertension and diabetes.  Table 3. Elderly people over the age of 60, regardless of age group, had the highest frequency of two or three conditions. Compared with people under the age of 70, the proportion of elderly people over the age of 70 with 4-5 chronic diseases increased signi cantly.

Discussion
In this study, we analyzed the prevalence of hypertension, diabetes, dyslipidemia, CHD and CKD and their multimorbidity status in the urban elderly population in northeastern China. We de ned the above ve diseases as chronic diseases. Within a sample of elderly individuals, we found that the prevalence of chronic diseases was high, with a prevalence of hypertension and dyslipidemia as high as 60%, followed by diabetes and CHD affecting more than 50% of men.
The prevalence of hypertension was 67.6% in men and 64.1% in women in our study. Wang et al. reported that the prevalence of hypertension was 76.4% among elderly individuals in rural areas of Shandong 8 , which was higher than our result. However, another study of elderly individuals showed that the prevalence of hypertension was 26.0% in Haikou, China, which was signi cantly lower than the above research results. This may be related to the region, since previous studies have con rmed that hypertension is related to living environments 21 . The awareness and controlled rates of hypertension among elderly individuals in this study were 77.0% and 61.0%, respectively, which were signi cantly better than the results for elderly hypertension in Hebei 22 . Awareness and controlled hypertension among subjects with hypertension were 82.1% and 51.8%, respectively, among US adults aged ≥18 in 2011 to 2012 23 . However, our awareness rate of hypertension was still lower than that of Americans, although the age range of the study population was different.
The prevalence of diabetes in elderly individuals was 63.3% in men and 59.7% in women; meanwhile, 82.1% of diabetic subjects were aware of their condition, and 68.4% had well-controlled glucose levels in the present study. Liu Miao et al. reported that in 2010, the prevalence of diabetes among the elderly was 24.8%, the awareness rate was 73.6%, and the controlled rate was 20.1% in Beijing 24 . Although the awareness and control rate of diabetes was better in our study than in previous studies, the increase in the prevalence of diabetes is still a problem that cannot be ignored.
Dyslipidemia is an independent risk factor for atherosclerotic cardiovascular disease and it is a common chronic disease among the elderly. Our study showed that the prevalence of dyslipidemia was 63.3% in men and 71.1% in women. According to the 2016 blood lipid control guidelines in China, the overall prevalence of dyslipidemia is 40.4% 25 . The blood lipid level tends to increase with age. A large-scale epidemiological study con rmed the above trends in China in 2010 26 . Wang et al. reported that the prevalence of dyslipidemia among elderly individuals in rural areas of Shandong was 54.2% 8 . Our results were signi cantly higher than those of the above studies. This may be related to higher levels of consumption of cooking oil or meat in the urban population, but further veri cation is needed.
We found the prevalence of CHD was 51.0% in men, while it was 44.8% in women, which is not only higher than that in a study of elderly people (24.5% and 22.8% in men and women) between June 2015 and November 2017 in Iran 27 but also higher than a study reporting 34% between June 2010 and July 2011 in rural Shandong in China 8 .
The overall crude prevalence of CKD was 14.9% in our study. This was higher than a previous study at 11.5%, based on a 45-year-old population in 2012 28 . In contrast, the prevalence of CKD estimated in our study was still well below the level of the USA in 2013 29 .
It was not surprising that the prevalence of the above chronic diseases was high because they are affected by current lifestyle and environmental factors. In addition, we also analyzed the multimorbidity of the elderly population. We found that the prevalence of multimorbidity was 75.4% in our sample. This ts within the range of the overall prevalence from a systematic review in China but is close to the high value of the range 30 . A recent multicenter study showed that the average frequency of multimorbidity was 69.3% among elderly individuals, and these data were from medical wards of tertiary-care hospitals in China. In addition, this multicenter study showed that the prevalence of multimorbidity was higher in the northern area (71.7%), which was similar to our results, compared to the south (66%) 31 . In another survey conducted in eastern China, the prevalence of multimorbidity was 90.5% in the rural elderly population, which was higher than in our study 8 . This may be related to the higher health awareness of urban residents than rural residents. It is worth mentioning that the inclusion and de nitions of chronic diseases in the above studies were not exactly the same, which would result in inaccurate comparisons.
This population-based study targeted elderly people living in an urban region in China and covered ve general chronic diseases. To our knowledge, this is the rst study about the prevalence of chronic diseases and multimorbidity among elderly individuals in urban areas of northeastern China. However, our study had some limitations. First, there were potential errors in self-reporting of chronic conditions, participant recall bias and interviewer bias. Second, the population aged above 80 years accounted for only a tiny proportion (4.6%) of the total sample. Third, the cross-sectional study design limited our ability to establish causal relationships. Furthermore, future studies should collect more information on chronic diseases in the elderly.

Conclusion
In conclusion, despite its potential limitations, this study provided important insights into the prevalence of ve chronic conditions and multimorbidity in an elderly population in northeastern China. Elderly people in northeastern China are exposed to health-harming behaviors, such as failure to control their weight, a high salt intake, and a lack of exercise. This baseline evidence may be helpful for identifying health priorities for this population; this knowledge could provide practical guidance for developing relevant health policies. However, the prevalence of chronic diseases and their associated factors in the target population should continue to be monitored in the long term.

Declarations
Ethics approval and consent to participate All of the participants provided written informed consent. This study protocol was approved by The First Hospital of Jilin University Ethics Committee. All participants consented to participate.

Consent for publication
Not Applicable.
Availability of data and material The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests
There were no competing interests.