Profiles of participants
Table 1 shows the demographic profiles of the part included in this study. Among the 664,926 participants, 42.76% were men and the mean age was 62.3 years (39–75 years). Moreover, 31.70% of the studied individuals exercised for ≥ 30 minutes, and 38.17% regularly walked or engaged in physical activity. Furthermore, 38.26% of the participants reported walking faster as compared to the other participants of the same sex and age. Altogether, 15.56% and 46.50% of the participants had a smoking history and drinking habits, respectively. The history of cerebrovascular disease, cardiovascular disease, chronic renal failure, or anemia was present in 3.49%, 5.40%, 0.77%, and 8.65% of the participants, respectively.
Classification of causes of death
All participants were followed up for 7 years; 8,051 of them died. The causes of their deaths are summarized in Table 2. Malignant neoplasm was the most common cause of death, accounting for 4,159 deaths (62.78% were men) and more than half of all deaths in both sexes. The second most common cause of death was circulatory system disease with 1,616 deaths (64.60% were men), accounting for approximately 20% of all deaths in both sexes. The third and fourth most common causes of death was injury, poisoning, or other external causes (920 deaths, 64.46% were men) and respiratory disease (437, 73.23% were men), respectively. Since deaths from malignant neoplasms include deaths related to respiratory disease, we extracted data of 826 deaths from malignant neoplasms of the bronchus and lungs [71.67% (n = 592) were men]. As a result, the total number of deaths from malignant and non-malignant neoplasms of the respiratory system was 1,263 (72.21% [n = 912] were men), accounting for 15.69% of all deaths (17.71% and 12.10% of all deaths in men and women, respectively).
Risk of deaths due to respiratory diseases
The causes of deaths from respiratory diseases, including malignant neoplasms, are shown in Table 3. Of the 1263 deaths, the most common cause was malignant neoplasm, followed by respiratory infections caused by viruses and bacteria (151 were men, 47.19%; 51 were women, 43.59%). Interstitial pulmonary disease was the third most common cause, followed by obstructive pulmonary disease.
Table 4 shows the results of the analysis for the risk of death from respiratory disease with or without malignant neoplasm in the respiratory tract. Death from respiratory disease, including malignant neoplasm, was significantly associated with sex, older age, lower body mass index (BMI), increased systolic blood pressure, no walking habit or physical activity, slow walking speed, smoking history, drinking habit, adequate sleep, history of cerebrovascular or cardiovascular disease, receiving treatment for hypertension or diabetes, increased levels of fasting blood glucose, hemoglobin A1c (HbA1c), aspartate aminotransferase (AST), UA, and creatinine (Cre), decreased level of high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and alanine aminotransferase (ALT), and proteinuria.
Deaths from respiratory disease excluding malignant neoplasms were significantly associated with sex, older age, lower BMI, decreased waist circumference, lower diastolic blood pressure, no weight gain of > 10 kg compared to the weight at 20 years of age, no exercise habit of > 30 minutes, no walking habit or physical activity, slow walking speed, history of cerebrovascular disease, cardiovascular disease, or chronic renal failure, receiving treatment for hypertension or diabetes, increased fasting blood glucose, HbA1c, AST, UA, and Cre levels, increased estimated glomerular filtration rate (eGFR), lower triglyceride (TG), HDL-C, and LDL-C levels, and proteinuria.
Deaths from malignant neoplasms in the respiratory tract were significantly associated with sex, aging, increased waist circumference, higher systolic blood pressure, slow walking speed, smoking history, drinking habits, adequate sleep, history of cerebrovascular or cardiovascular disease, treatment for hypertension or diabetes, increased fasting blood glucose, HbA1c, TG, AST, hemoglobin, hematocrit, UA, and creatinine levels, lower HDL-C and LDL-C levels, and proteinuria.
The independent risk factors of death from respiratory disease with or without a malignant neoplasm in the respiratory tract was examined through a Cox proportional hazards analysis (Table 5). For deaths from respiratory disease, including malignant neoplasm, the independent risk factors were male sex, older age, lower BMI, no walking habit or physical activity, slow walking speed, smoking history, no drinking habit, history of cerebrovascular disease, increased HbA1c and UA levels, decreased LDL-C level, and proteinuria. For deaths from respiratory disease, excluding malignant neoplasm, the independent risk factors were male sex, older age, lower BMI, slow walking speed, history of cerebrovascular disease or chronic renal failure, increased HbA1c and UA levels, increased eGFR, decreased LDL-C level, and proteinuria. For deaths from malignant neoplasm in the respiratory tract, the independent risk factors were male sex, older age, slow walking speed, smoking history, increased HbA1c level, and decreased hemoglobin level.