Cui H et al. Cardiovascular diseases in COPD heart disease. Lastly, the early diagnosis and standardized treatment for COPD patients made a positive impact on the prevention and control of ischemic heart disease. In addition, exposure to tobacco smoke, occupational dust and air pollution are common risk factors for CVD and COPD.[17,18] Exposure to such risk factors in females in China, because of their increased social status, may have led to the gradual increase in the proportion of women with COPD and CVD in the recent decade. The prevalence of arrhythmias was relatively stable except for a rise in 2003~2004. The number of males with arrhythmia, as a complication, decreased year on year, with a slight increase in the number of women with arrhythmias. The prevalence of arrhythmias in COPD patients also increased with increasing age. One important factor is that smoking and aging may be interrelated because they cause cell damage, which may increase the risk of complications in COPD.[7,8] Arrhythmia, often accompanied COPD or CVD, was not determined to be an independent disorder. It is associated with the instability of myocardial cells, damage to cardiac conduction fibers, or changes in the environment of cells. In addition to chronic hypoxia, oxidative effects, and inflamma- tion in COPD patients, the occurrence of ischemic heart disease, heart failure and/or hypertension would give rise to different types of arrhythmia.[19] Therefore, arrhythmias are closely related to the development of COPD and CVD. A higher incidence of arrhythmias has been reported in COPD patients. Hypoxemia, infection, heart failure, acid- base imbalance and electrolyte disturbances induce and aggravate arrhythmia. The prevalence of arrhythmias in COPD patients increased with age, aggravation of heart dysfunction, and coronary heart disease. It has been suggested that respiratory failure, cardiac dysfunction, coronary heart disease, hypokalemia, and old age are important factors for arrhythmia in COPD patients. Arrhythmia is also closely related to the prognosis of COPD.[20] According to worldwide data, the prevalence of heart failure for the general population is 1.5%~2%, but for those aged ≥ 65 years, it is 6%~10%. The prevalence of adults with heart failure was 0.9%. In males it was 0.7% and in females it was 1%. In the past 40 years, the prevalence of deaths caused by heart failure has increased sixfold. Heart failure has become an important public health issue in the 21st century.[21] In Western countries, the prevalence of heart failure in COPD patients is about 20%. The prevalence of COPD in heart failure patients can be as high as 20%~30%, similar to the values of the present study.[22] In hospitalized patients, heart failure in elderly patients with COPD is associated 9 with a greater risk of death compared with age-matched patients with heart failure alone or patients with COPD.[23] The study showed that the older the patient, the higher was the prevalence of heart failure in COPD patients. This was similar to the prevalence of other types of CVD, and the number of female patients with heart failure was higher than the number of males with heart failure (P < 0.05). The ECCO study showed that heart failure, osteoporosis, edema, hypertension and diabetes without complications were higher in female COPD patients than in male COPD patients.[11] The prevalence of heart failure was in a downward trend over the decade with a break in the trend in 2003~2004. The reasons included poor awareness of patients; a low detection rate before 2003; extremely rapid economic development; active and passive smoking in 2003~2004; and because awareness of universal healthcare and social security increased after 2005. The prevalence in males over 10 years tended to decrease, whereas in women it increased. In addition to the prevalence of sex-based differences, the level of medical technology increased, exposure to passive smoking and occupational exposure for women increased, social and psychological stress increased, and the gradual loss of estrogen-protective factors were all associated with the increase in the proportion of women with COPD who had heart failure.[25] 5 Study limitations The patients involved in the present study were urban residents. As a retrospective investigation, the study did not investigate treatment or smoking status that could affect the prevalence of CVD. Acknowledgements This work was supported by a grant from Medical and Health Research Funds of PLA (NO.06MA29). References 1 2 3 Cazzola M, Bettoncelli G, Sessa E, et al. Prevalent ratio of comorbidities in patients with chronic obstructive pulmonary disease. Respiration 2010; 80: 112–119. Chugh SS, Reinier K, Teodorescu C, et al. Epidemiology of sudden cardiac death: clinical and research implications. Prog Cardiovasc Dis 2008; 51: 213–228. Hanrahan JP, Grogan DR, Baumgartner RA, et al. Arrhythmias in patients with chronic obstructive pulmonary disease (COPD): occurrence frequency and the effect of http://www.jgc301.com; jgc@mail.sciencep.com | Journal of Geriatric Cardiology