Objectives Abnormal eating behaviour and metabolic parameters are increasingly recognised as important components of neurodegenerative disease and may contribute to survival. It has previously been established that behavioural variant frontotemporal dementia (bvFTD) is associated with abnormal eating behaviour. In this study, it was hypothesised that bvFTD might also be associated with altered energy expenditure.

Methods A cohort of 19 patients with bvFTD, 13 with Alzheimer’s disease (AD) and 16 (age- and sex- matched) healthy controls were studied using Actiheart devices (CamNtech, UK) to assess resting and stressed heart rate. Actiheart devices were fitted for 7 days to measure sleeping heart rate, activity levels, and resting, active and total energy expenditure. Using high resolution structural MRI the neural correlates of increased resting heart rate were investigated including cortical thickness and region of interest analyses.

Results In bvFTD, resting (p=0.001), stressed (p=0.037) and sleeping heart rate (p=0.038) were increased compared with controls, and resting heart rate (p=0.020) compared with AD patients. BvFTD was associated with decreased activity levels compared with controls (p=0.002) and increased resting energy expenditure (p=0.045) and total energy expenditure (p=0.035). Increased resting heart rate correlated with behavioural (Cambridge Behavioural Inventory) and cognitive measures (Addenbrooke’s Cognitive Examination). Increased resting heart rate in bvFTD correlated with atrophy involving the mesial temporal cortex, insula, and amygdala, regions previously suggested to be involved exclusively in social and emotion processing in frontotemporal dementia.

Conclusions These neural correlates overlap the network involved in eating behaviour in FTD suggesting, a complex interaction between eating behaviour, autonomic function and energy homeostasis. The present study suggests that increased heart rate and autonomic changes are prevalent in bvFTD, and are associated with changes in energy expenditure. An understanding of these changes and neural correlates may have potential relevance to disease progression and prognosis.