La relazione tra metabolismo energetico basale e mortalità nel Baltimore Longitudinal Study of Aging

Introduction. Despite longstanding controversies from animal studies on the relationship between basal metabolic rate and longevity, whether basal metabolic rate is a risk factor for mortality has never been tested in humans. We evaluate the longitudinal changes in basal metabolic rate and the relationship between basal metabolic rate and mortality in the Baltimore Longitudinal Study of Aging participants. Methods. Basal metabolic rate and medical information were collected at the study entry and approximately every 2 years in 1,227 participants (972 men) over a 40-year follow-up. Basal metabolic rate, expressed as kcal/m²/h, was estimated from the basal O ₂ consumption and CO₂ production measured by open-circuit method. Data on all-cause and specific-cause mortality were also obtained. Results. Basal metabolic rate declined with age at a rate that accelerated at older ages. Independent of age, participants who died had a higher basal metabolic rate compared to those who survived. Basal metabolic rate was a significant risk factor for mortality independent of secular trends in mortality and other well-recognized risk factors for mortality, such as age, body mass index, smoking, white blood cell count, and diabetes. Basal metabolic rate was nonlinearly associated with mortality. The lowest mortality rate was found in the basal metabolic rate range 31.3-33.9 kcal/m2/h. Participants with basal metabolic rate in the range 33.9-36.4 kcal/m2/h and above the threshold of 36.4 kcal/m2/h experienced 28% (hazard ratio: 1.28; 95% confidence interval, 1.02-1.61) and 53% (hazard ratio: 1.53; 95% confidence interval, 1.19-1.96) higher mortality risk compared to participants with basal metabolic rate 31.3-33.9 kcal/m2/h. Discussion. We confirm previous findings of an age-related decline of basal metabolic rate. In our study, a blunted age-related decline in basal metabolic rate was associated with higher mortality, suggesting that such condition reflects poor health status.