Being Underweight In Mid To Late Life Associated With Increased Risk Of Dementia, New Study Suggests

Middle-aged and older people who are underweight with a Body Mass Index (BMI) of less than 20 kg/m2 are a third more likely to develop dementia than people of similar age with a healthy BMI, according to new research published in The Lancet Diabetes & Endocrinology journal today (Friday 10 April 2015).

Researchers based at the London School of Hygiene & Tropical Medicine and OXON Epidemiology analysed data from almost 2 million people in the Clinical Practice Research Datalink (CPRD), a large database of patient information recorded during routine general practice over nearly 20 years, representing around 9 per cent of the UK population. 

The report highlights that evidence shows:

  • People who were underweight in middle and older age were a third (34 per cent) more likely to be diagnosed with dementia than those of a healthy weight, and this increased risk of dementia persisted even 15 years after the underweight was recorded.
  • As participants’ BMI between 40 and 80 years of age increased, the risk of dementia reduced, with very obese people (BMI greater than 40 kg/m2) 29 per cent less likely to get dementia than people in the normal weight range.

Dr Doug Brown, Director of Research and Development at Alzheimer’s Society, said:

‘We don’t yet know enough about the link between body weight and dementia. Previous research has suggested that being overweight in midlife increases risk of developing the condition and yet this study suggests that it may actually be protective. This study of almost 2 million people also reports that being underweight in later years could increase risk of developing the condition by a third.

This mixed picture highlights the difficulty of conducting studies into the complex lifestyle risk factors for dementia and reinforces the need for further research so we can identify the most important risk factors. While the evidence on body weight and dementia is unclear, we know that people can make positive lifestyle choices to keep their brains healthy by taking regular exercise, not smoking and following a healthy balanced diet.’