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Table 1 Characteristics of the study population, by BMI assessment type and by BMI category

From: Mortality risk associated with underweight: a census-linked cohort of 31,578 individuals with up to 32 years of follow-up

  Measured BMI Self-reported BMI
  Body mass index category (kg/m2) Body mass index category (kg/m2)
  <18.5 18.5- <25 25- <30 ≥30 Missings (n) <18.5 18.5- <25 25- <30 ≥30 Missings (n)
Participants (n) 348 8647 5951 1805   597 9274 4050 906  
Participants (in % of total n, by BMI assessment type) 2.1 51.6 35.5 10.8   4.0 62.5 27.3 6.1  
Women (%) 87.9 59.7 38.0 47.3   91.1 58.8 35.7 47.7  
Mean BMI (kg/m2) 17.7 22.3 27.1 32.8   17.6 22.1 26.9 33.0  
Mean follow-up time (years) 23.3 22.3 20.2 18.8   16.9 17.1 16.7 15.9  
Mean age (years) 41.0 43.4 48.8 52.1   40.4 44.1 49.9 52.1  
Mortality           
 All-cause           
 Deaths§ (n) 57 1526 1516 615   73 1173 851 243  
 Person-years (py) 8096 192739 120456 33840   10055 158996 67575 14468  
 Age-standardized rate (per 100000 py) 909 800 915 1117   1059 799 924 1090  
 Cardiovascular diseases (CVD)           
 Deaths (n) 16 468 529 251   18 407 307 96  
 Deaths (in % of all-cause deaths) 28.1 30.7 34.9 40.8   24.7 34.7 36.1 39.5  
 Age-standardized rate (per 100000 py) 282 269 321 464   342 294 332 437  
 Cancer           
 Deaths (n) 17 567 542 205   27 427 293 73  
 Deaths (in % of all-cause deaths) 29.8 37.2 35.8 33.3   37.0 36.4 34.4 30.0  
 Age-standardized rate (per 100000 py) 230 263 299 359   386 264 301 321  
 Respiratory diseases           
 Deaths (n) 3 91 77 28   2 69 49 20  
 Deaths (in % of all-cause deaths) 5.3 6.0 5.1 4.6   2.7 5.9 5.8 8.2  
 Age-standardized rate (per 100000 py) 54 51 48 52   29 50 50 90  
 External causes           
 Deaths (n) 10 121 92 30   10 68 39 6  
 Deaths (in % of all-cause deaths) 17.5 7.9 6.1 4.9   13.7 5.8 4.6 2.5  
 Age-standardized rate (per 100000 py) 174 63 75 58   109 48 49 34  
 Other           
 Deaths (n) 11 265 265 98   16 198 157 48  
 Deaths (in % of all-cause deaths) 19.3 17.4 17.5 15.9   21.9 16.9 18.5 19.8  
 Age-standardized rate (per 100000 py) 169 148 166 177   192 140 185 209  
Covariates           
 Smoking status°      31      19
 Never smokers (%) 54.5 47.7 45.1 51.7   46.1 46.6 40.7 44.5  
 Former smokers (%) 9.5 14.5 20.6 21.2   13.1 19.4 25.8 27.1  
 Current light smokers (%) 21.0 21.7 18.4 15.0   25.3 20.3 18.6 14.8  
 Current heavy smokers (%) 15.0 16.1 15.9 12.1   15.4 13.7 14.9 13.6  
 Healthy eating* (%) 77.3 71.6 68.7 66.3 23 68.3 67.1 64.9 65.6 368
 Sport      334      458
 Daily (%) 6.7 6.3 5.3 3.2   6.7 6.5 6.7 7.1  
 Several times per week (%) 11.1 17.6 14.8 8.6   26.1 30.2 25.5 20.1  
 Once per week (%) 24.4 24.8 20.7 13.7   22.6 23.6 20.0 16.7  
 Less than once per week (%) 57.9 51.3 59.2 74.6   44.6 39.7 47.8 56.1  
 Education      29      185
 Tertiary (%) 6.9 6.8 5.0 3.9   9.6 8.2 6.0 3.8  
 Upper secondary (%) 15.6 14.1 9.8 6.6   13.9 15.0 14.6 10.8  
 Secondary (%) 54.8 48.8 46.4 40.8   62.8 57.2 51.8 47.7  
 Mandatory (%) 22.8 30.3 38.8 48.7   13.7 19.5 27.6 37.6  
  1. §38 participants with missing information on cause of death. °Current light smokers: <20 cigarettes or 10 cigarillos or 10 pipes or 5 "stumpen" or 5 cigars a day. Current heavy smokers: ≥20 cigarettes or 10 cigarillos or 10 pipes or 5 "stumpen" or 5 cigars a day. *Defined as follows: MONICA, NRP 1A and SOMIPOPS: regularly eating three main meals per day; SHS 92/93: eating fruits and vegetables at least once per day. 31,578 participants (25–74 years at baseline) of Swiss MONICA, NRP1A, SOMIPOPS and SHS 92/93. Measured BMI: Swiss MONICA: 9,837 part. NRP 1A: 6,914 part. Self-reported BMI: SOMIPOPS: 3,503 part. SHS 92/93: 11,324 part.