Body mass index (BMI) was calculated as body weight (kg) divided by body height squared (m2). Educational level was indicated based on the highest education qualification attained, and categorised into 3 groups: low education (never been to school, or elementary schooling only); medium education (secondary schooling or lower/intermediate vocational schooling); and high education (higher vocational schooling or university). Marital status was assessed by a closed question with the following categories: married, living with partner (HELIUS)/registered partnership (LASA), never married, divorced, widowed. Smoking status was categorized into never, past or current smoker.
Protein intake was expressed in grams per kilogram of adjusted body weight per day (g/kg adjusted BW/d). We applied adjusted body weight because in overweight persons, much ‘extra weight’ is adipose tissue, while underweight persons require extra protein to built muscle tissue. Adjusted BMI was calculated for those with a BMI >25 kg/m2 (age ≤70 y) or >27 kg/m2 (age >70 y) by applying the body weight corresponding to a BMI of respectively 25 or 27 kg/m2. For those with a BMI <18.5 kg/m2 (age ≤70 y) or <22.0 kg/m2 (age >70 y) body weight corresponding to a BMI of respectively 18.5 or 22 kg/m2 was applied [12 (link)]. Protein intake was classified as either normal/high (>1.0 g/kg adjusted BW/d) or low (≤1.0 g/kg adjusted BW/d) based on increasing evidence and consensus that a protein intake of >1.0 g/kg adjusted BW/d in old age has health benefits [2 (link), 6 (link), 10 (link)]. A sensitivity analysis was performed with low protein intake defined as ≤0.8 g/kg adjusted BW/d.
Baseline participant characteristics were presented as mean with standard deviation (± SD), median with interquartile range (IQR) or frequency (%). Statistical analyses were performed using SPSS Statistics version 23 (IBM Corp., Armonk, NY, USA).
Protein intake was expressed in grams per kilogram of adjusted body weight per day (g/kg adjusted BW/d). We applied adjusted body weight because in overweight persons, much ‘extra weight’ is adipose tissue, while underweight persons require extra protein to built muscle tissue. Adjusted BMI was calculated for those with a BMI >25 kg/m2 (age ≤70 y) or >27 kg/m2 (age >70 y) by applying the body weight corresponding to a BMI of respectively 25 or 27 kg/m2. For those with a BMI <18.5 kg/m2 (age ≤70 y) or <22.0 kg/m2 (age >70 y) body weight corresponding to a BMI of respectively 18.5 or 22 kg/m2 was applied [12 (link)]. Protein intake was classified as either normal/high (>1.0 g/kg adjusted BW/d) or low (≤1.0 g/kg adjusted BW/d) based on increasing evidence and consensus that a protein intake of >1.0 g/kg adjusted BW/d in old age has health benefits [2 (link), 6 (link), 10 (link)]. A sensitivity analysis was performed with low protein intake defined as ≤0.8 g/kg adjusted BW/d.
Baseline participant characteristics were presented as mean with standard deviation (± SD), median with interquartile range (IQR) or frequency (%). Statistical analyses were performed using SPSS Statistics version 23 (IBM Corp., Armonk, NY, USA).
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