Table 1 Operationalisation of frailty used in the current study (modified Fried criteria)

1. Low gait speed (slowness)

Time to walk 15 feet (4.57 m) above a cut-off value stratified by gender and height:

Time to walk 15 feet (4.57 m) above a cut-off value stratified by gender and height (same criteria used by Fried et al. [17])

Men

Cut-off

Height ≤ 173 cm

 ≥ 7 s

Height > 173 cm

 ≥ 6 s

Women

Height ≤ 159 cm

 ≥ 7 s

Height > 159 cm

 ≥ 6 s

2. Low muscle strength (weakness)

Isometric handgrip test below a cut-off value stratified by gender and BMI:

Isometric handgrip test below a cut-off value stratified by gender and BMI (same criteria used by Fried et al. [17])

Men

Cut-off

BMI ≤ 24

 ≤ 29 kg

BMI: 24.1 – 26

 ≤ 30 kg

BMI: 26.1 – 28

 ≤ 30 kg

BMI > 28

 ≤ 32 kg

Women

BMI ≤ 23

 ≤ 17 kg

BMI: 23.1 – 26

 ≤ 17.3 kg

BMI: 26.1 – 29

 ≤ 18 kg

BMI > 29

 ≤ 21 kg

3. Low physical activity (inactivity)

Kcal/week of physical activity below a cut-off value stratified by gender (calculated using the standardised algorithm of the Short-Form Minnesota Leisure Time Activity Questionnaire):

Kcal/week of physical activity below a cut-off value stratified by gender (calculated using the standardised algorithm of the Short-Form International Physical Activity Questionnaire):

Men

 < 383 kcal/week

Men

 < 383 kcal/week

Women

 < 270 kcal/week

Women

 < 270 kcal/week

4. Poor endurance (exhaustion)

Answering ‘a moderate amount of the time’ or ‘most of the time’ to the following two statements from the CES-D questionnaire: 1) ‘I felt that everything I did was an effort’, 2) ‘I could not get going’

Vitality score < 55 using the SF-36 questionnaire [25]

5. Weight loss (shrinkage)

Unintended weight loss ≥ 10 lbs (4.54 kg) in the previous 12 months

Unintended weight loss ≥ 10 lbs (4.54 kg) in the previous 12 months (same criteria used by Fried et al. [17])