| dc.description.abstract | Globally, there has been a substantial rise in the prevalence of obesity amongst
older persons (≥65 years) since the 1980s. Conflicting evidence exists on the
impact of this trend for health outcomes. A 2013 meta-analysis documented no
statistical difference for mortality between those within the body mass index
(BMI) defined Obese-1 (30.0-34.9 kg/m2) range and those within the
conventional BMI Normal (18.5-24.9) range, sparking vigorous debate. The
reduced or similar mortality risks for those within the BMI Obese-1 range
relative to those within the BMI Normal range has been termed the “obesity
paradox”. Clarifying associations of obesity with health outcomes could have
implications for intervention in later life. I aimed to examine this paradox by
assessing the length of follow-up, the BMI referent group, the inclusion of
smokers plus those with conditions associated with weight loss, and alternative
measures of adiposity.
I analysed >955,000 electronic health records from the UK Clinical Practice
Research Datalink for patients aged ≥60 years. I showed reduced mortality risks
for those within the BMI Obese-1 range relative to those within the BMI Normal
range across each age group. Mortality risks were reversed after restricting the
analysis to ‘healthier agers’, demonstrating that the paradox is partly explained
by the inclusion of smokers, adults with conditions associated with weight loss,
and the chosen BMI referent group. Similarly, I document no support for
reduced dementia risks for those within the BMI Obese-1 range. Additionally,
there was an increased risk for incident of coronary heart disease and diabetes
for those within the BMI Obese-1 range.
BMI does not capture body composition changes with ageing. I found additional
adiposity measures improved the mortality prediction compared to BMI only
using the UK Biobank comprising >200,000 older volunteers. Mortality risks
were increased for those who were centrally obese across the BMI Normal to
Obese-1 range.
In conclusion, I have shown the heterogeneity of older adults can result in
disparate risk estimates for the association between BMI and health outcomes. I
provide additional evidence that reliance on BMI measures only may miss those
at increased risk for health outcomes due to central adiposity. My results
provide no support, in relatively healthy older adults, for the hypothesised
obesity paradox in later life. | en_GB |
