Association of body mass index and weight change with pneumonia mortality in a Japanese population: Japan Public Health Center-based Prospective Study.

Abstract

Accumulating evidence suggests that pneumonia mortality is lower for individuals with high body mass index (BMI) compared to normal BMI, but it remains unclear whether weight change during adulthood influences subsequent mortality due to pneumonia in Asian populations, who have a relatively lean body mass. This study aimed to examine the association of BMI and weight change over 5 years with the subsequent risk of pneumonia mortality in a Japanese population. The present analysis included 79,564 Japan Public Health Center (JPHC)-based Prospective Study participants who completed a questionnaire between 1995 and 1998 were followed for death through 2016. BMI was categorized into four groups: underweight (<18.5 kg/m2), normal weight (BMI: 18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obese (BMI: ≥30.0 kg/m2). Weight change was defined as the difference of body weight between questionnaire surveys with a 5-year interval. Cox proportional hazards regression was used to estimate hazard ratios of baseline BMI and weight change for pneumonia mortality. During a median follow-up of 18.9 y, we identified 994 deaths from pneumonia. Compared with participants with normal weight, an elevated risk was observed among those who were underweight (hazard ratio = 2.29, 95% confidence interval [CI]: 1.83-2.87), whereas a decreased risk was found among those who were overweight (hazard ratio = 0.63, 95% CI: 0.53-0.75). Regarding weight change, the multivariable-adjusted hazard ratio (95% CI) of pneumonia mortality for a weight loss of 5 kg or more versus a weight change of less than 2.5 kg was 1.75 (1.46-2.10), whereas that for a weight gain of 5 kg or more was 1.59 (1.27-2.00). Underweight and greater weight change was associated with an increase in the risk of pneumonia mortality in Japanese adults.