Frailty in old age risk linked to midlife obesity

Mid-life obesity is linked to an increased risk of physical frailty in older age, according to Norwegian research published today.

Mounting evidence suggests obese older adults may be at increased risk because being significantly overweight aggravates the age-related decline in muscle strength, aerobic capacity, and physical function.

Because few studies have tracked weight changes and frailty risk over the long term, researchers from the University of Oslo analysed the population-based Tromsø Study to find out if general (BMI) and abdominal (waist circumference) obesity, separately and jointly, could affect the risk of pre-frailty/frailty.

The Tromsø Study consists of seven survey waves of 45,000 residents from Tromsø, aged 25 to 99, carried out between 1974 and 2015-16.

The current study, reported in the latest edition of *BMJ Open*, drew on data from waves four (1994-5) to seven (2015-16), with the final analysis included 4,509 people aged 45 or older.

The average age at baseline was 51 and the average monitoring period lasted 21 years.

A BMI of less than 18.5 was categorised as underweight, normal as 18.5-24.9, overweight as 25–29.9, and obesity as 30 and above.

Normal waist circumference was measured at 94 cm or less for men and 80 cm or less for women, while moderately high was classed as 95–102 cm for men and 81–88 cm for women. High was classed as above 102 cm for men and above 88 cm for women.

By 2015-16, 28% of participants were categorised pre-frail, 1% were frail, and 70.5% were strong. Nearly 51% of those who were strong and 55% of those categorised as pre-frail were women.

While participants in both the strong and pre-frail/frail groups put on weight and expanded their waistlines during the monitoring period, there were higher proportions of participants with normal BMIs and waistlines at the start of the monitoring period in the strong group.

Those who were assessed by BMI alone as obese in 1994 were nearly 2.5 times more likely to be pre-frail/frail at the end of the monitoring period than those with a normal BMI.

Those with a moderately high or high waist circumference, to start off with were 57% and twice respectively as likely, to be pre-frail/frail than those with a normal waistline.

Those who started off with a normal BMI but moderately-high waist circumference, or who were overweight but had a normal waistline, were not significantly more likely to be pre-frail/frail at the end of the monitoring period.

However, individuals who were both obese and who had a moderately-high waist circumference at the start of the monitoring period were more likely to be pre-frail/frail at the end of the monitoring period.

The researchers also said there were increased risks of pre-frailty/frailty in individuals who put on weight and among those whose waistlines expanded than in those whose weight and waistlines remained the same throughout.

The team writes this is an observational study that did not track potentially influential changes in lifestyle, diet, and friendship networks, which might have occurred during the monitoring period.

However, the findings were still significant for participants with baseline obesity and higher waist circumference when the over 60s were excluded from the analysis. Few underweight people were included in the study.

There are also some plausible biological explanations for their findings, including the increased inflammatory capacity of fat cells and their infiltration into muscle cells, heightening the risk of frailty, they explain.

Nevertheless, they conclude: “In the context where the population is rapidly ageing and the obesity epidemic is rising, growing evidence recognises the subgroup of ‘fat and frail’ older individuals in contrast to viewing frailty only as a wasting disorder.”

Meanwhile, research published in the latest *Journal of Epidemiology & Community Health* has found the amount of time spent in moderate and vigorous physical activity every day is linked to mid-life brain power.

Previous studies have linked daily moderate and vigorous physical activity (MVPA) to health, but few have included time spent asleep.

Researchers at UCL, UK, analysed data from the 1970 British Cohort Study, which comprises people born in England, Scotland, and Wales in 1970 and whose health was tracked throughout childhood and adulthood.

In 2016-18, 8581 participants had reached the ages of 46-47, at which point they were asked to fill in detailed health, background, and lifestyle questionnaires, and to wear an activity tracker for up to seven days and for at least 10 consecutive hours a day.

They took cognitive tests for verbal memory and executive function, with scores for each test producing an overall global score for memory and executive function.

The final analysis included 4481 participants, just over half of whom (52%) were women.

Analysis showed that participants clocked up an average of 51 minutes of MVPA, 5 hours 42 minutes of light intensity physical activity, nine hours 16 minutes of sedentary behaviours, and eight hours 11 minutes of sleep over a 24-hour period.

Time spent in MVPA relative to other types of behaviour was positively associated with cognitive performance after adjusting for educational attainment and workplace physical activity. But additional adjustment for health issues weakened these associations.

Sedentary behaviour relative to sleep and light physical intensity activity was also positively associated with cognitive performance.

The associations were stronger for executive function than they were for memory.

Although this is an observational study, the researchers conclude: “This robust method corroborates a critical role for MVPA in supporting cognition, and efforts should be made to bolster this component of daily movement.”

Uchai S, Frost Andersen L, Arnesdatter Hopstock L et al. Body mass index, waist circumference and pre-frailty/frailty: the Tromsø study 1994?2016. *BMJ Open* 24 January 2023; doi 10.1136/bmjopen-2022-065707


Mitchell JJ, Blodgett JM, Chastin SFM et al. Exploring the associations of daily movement behaviours and mid-life cognition: a compositional analysis of the 1970 British Cohort Study. *Journal of Epidemiology & Community Health* 24 January 2023; doi 10.1136/jech-2022-219829

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