TY - JOUR
T1 - Change in Body Mass Index Associated With Lowest Mortality in Denmark, 1976-2013
AU - Afzal, Shoaib
AU - Tybjærg-Hansen, Anne
AU - Jensen, Gorm B
AU - Nordestgaard, Børge G
PY - 2016/5/10
Y1 - 2016/5/10
N2 - Importance: Research has shown a U-shaped pattern in the association of body mass index (BMI) with mortality. Although average BMI has increased over time in most countries, the prevalence of cardiovascular risk factors may also be decreasing among obese individuals over time. Thus, the BMI associated with lowest all-cause mortalitymay have changed. Objective: To determine whether the BMI value that is associated with the lowest all-cause mortality has increased in the general population over a period of 3 decades. Design, Setting, and Participants: Three cohorts from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13 704) and 1991-1994 (n = 9482) and the Copenhagen General Population Study in 2003-2013 (n = 97 362). All participants were followed up from inclusion in the studies to November 2014, emigration, or death, whichever came first. Exposures: For observational studies, BMI was modeled using splines and in categories defined by the World Health Organization. Body mass index was calculated as weight in kilograms divided by height in meters squared. Main Outcomes and Measures: Main outcomewas all-cause mortality and secondary outcomes were cause-specific mortality. Results: The number of deaths during follow-up was 10 624 in the 1976-1978 cohort (78% cumulative mortality; mortality rate [MR], 30/1000 person-years [95% CI, 20-46]), 5025 in the 1991-1994 cohort (53%; MR, 16/1000 person-years [95% CI, 9-30]), and 5580 in the 2003-2013 cohort (6%; MR, 4/1000 person-years [95% CI, 1-10]). Except for cancer mortality, the association of BMI with all-cause, cardiovascular, and other mortality was curvilinear (U-shaped). The BMI associated with the lowest all-cause mortality increased by 3.3 from the 1976-1978 cohort compared with the 2003-2013 cohort. (Table Presented) The multivariable-adjusted hazard ratios for all-cause mortality for BMI of 30 or more vs BMI of 18.5 to 24.9 were 1.31 (95% CI, 1.23-1.39;MR, 46/1000 person-years [95% CI, 32-66] vs 28/1000 person-years [95% CI, 18-45]) in the 1976-1978 cohort, 1.13 (95% CI, 1.04-1.22; MR, 28/1000 person-years [95% CI, 17-47] vs 15/1000 person-years [95% CI, 7-31]) in the 1991-1994 cohort, and 0.99 (95% CI, 0.92-1.07;MR, 5/1000 person-years [95% CI, 2-12] vs 4/1000 person-years [95% CI, 1-11]) in the 2003-2013 cohort. Conclusions and Relevance: Among 3 Danish cohorts, the BMI associated with the lowest all-cause mortality increased by 3.3 from cohorts enrolled from 1976-1978 through 2003-2013. Further investigation is needed to understand the reason for this change and its implications.
AB - Importance: Research has shown a U-shaped pattern in the association of body mass index (BMI) with mortality. Although average BMI has increased over time in most countries, the prevalence of cardiovascular risk factors may also be decreasing among obese individuals over time. Thus, the BMI associated with lowest all-cause mortalitymay have changed. Objective: To determine whether the BMI value that is associated with the lowest all-cause mortality has increased in the general population over a period of 3 decades. Design, Setting, and Participants: Three cohorts from the same general population enrolled at different times: the Copenhagen City Heart Study in 1976-1978 (n = 13 704) and 1991-1994 (n = 9482) and the Copenhagen General Population Study in 2003-2013 (n = 97 362). All participants were followed up from inclusion in the studies to November 2014, emigration, or death, whichever came first. Exposures: For observational studies, BMI was modeled using splines and in categories defined by the World Health Organization. Body mass index was calculated as weight in kilograms divided by height in meters squared. Main Outcomes and Measures: Main outcomewas all-cause mortality and secondary outcomes were cause-specific mortality. Results: The number of deaths during follow-up was 10 624 in the 1976-1978 cohort (78% cumulative mortality; mortality rate [MR], 30/1000 person-years [95% CI, 20-46]), 5025 in the 1991-1994 cohort (53%; MR, 16/1000 person-years [95% CI, 9-30]), and 5580 in the 2003-2013 cohort (6%; MR, 4/1000 person-years [95% CI, 1-10]). Except for cancer mortality, the association of BMI with all-cause, cardiovascular, and other mortality was curvilinear (U-shaped). The BMI associated with the lowest all-cause mortality increased by 3.3 from the 1976-1978 cohort compared with the 2003-2013 cohort. (Table Presented) The multivariable-adjusted hazard ratios for all-cause mortality for BMI of 30 or more vs BMI of 18.5 to 24.9 were 1.31 (95% CI, 1.23-1.39;MR, 46/1000 person-years [95% CI, 32-66] vs 28/1000 person-years [95% CI, 18-45]) in the 1976-1978 cohort, 1.13 (95% CI, 1.04-1.22; MR, 28/1000 person-years [95% CI, 17-47] vs 15/1000 person-years [95% CI, 7-31]) in the 1991-1994 cohort, and 0.99 (95% CI, 0.92-1.07;MR, 5/1000 person-years [95% CI, 2-12] vs 4/1000 person-years [95% CI, 1-11]) in the 2003-2013 cohort. Conclusions and Relevance: Among 3 Danish cohorts, the BMI associated with the lowest all-cause mortality increased by 3.3 from cohorts enrolled from 1976-1978 through 2003-2013. Further investigation is needed to understand the reason for this change and its implications.
KW - Aged
KW - Aged, 80 and over
KW - Body Height
KW - Body Mass Index
KW - Body Weight
KW - Cardiovascular Diseases
KW - Cause of Death
KW - Cohort Studies
KW - Denmark
KW - Female
KW - Humans
KW - Male
KW - Middle Aged
KW - Neoplasms
KW - Proportional Hazards Models
KW - Journal Article
KW - Research Support, Non-U.S. Gov't
U2 - 10.1001/jama.2016.4666
DO - 10.1001/jama.2016.4666
M3 - Journal article
C2 - 27163987
SN - 0098-7484
VL - 315
SP - 1989
EP - 1996
JO - J A M A: The Journal of the American Medical Association
JF - J A M A: The Journal of the American Medical Association
IS - 18
ER -
