Elevated Crude Mortality in Obese Chronic Kidney Disease Patients with Loss of Exercise Habit: A Cohort Study of the Japanese General Population

OBJECTIVE: The relationship between obesity and risk of death in chronic kidney disease (CKD) patients remains controversial. In addition, no clear evidence has been accumulated regarding whether or not exercise improves mortality in CKD patients. METHODS: The original cohort was based on a Japanese general population of 685,889 people from 40 to 74 years old who had undergone annual specific health checkups. The number of all-cause deaths during follow-up (mean, 4.7 years) in this study was 1,490. Information on walking and exercise habits was obtained by questionnaires. The study population was divided into 4 categories by the combination of CKD and obesity [body mass index (BMI) ≥25.0 kg/m(2)]. Changes in the BMI and walking and exercise habits were determined by results for the first year and following year. RESULTS: Obese CKD patients with weight gain (BMI increase by more than +1.0 kg/m(2)/year) showed a higher crude mortality (1.32%) than those with a stable BMI (within ±1.0 kg/m(2)/year; 0.69%). In the obese CKD population, mortality was higher with loss of exercise habits (0.96%) than in those continuously maintaining exercise habits (0.52%). The age- and sex-adjusted hazard ratio for all-cause death was 2.23 in the group with weight gain compared to the group with stable weight (p<0.01) and 2.08 in the group with loss of exercise habits compared to those who maintained exercise habits (p<0.01). CONCLUSION: This observational cohort study suggested that loss of exercise habits as well as weight gain of more than 1 kg/m(2)/year might worsen all-cause mortality in the obese CKD population.