Body Mass Index Trajectories in Relation to Change in Lean Mass and Physical Function: The Health, Aging and Body Composition Study.
OBJECTIVE
To examine body mass index (BMI) trajectories with change in lean mass and physical function in old age.


METHODS
Prospective cohort study.


METHODS
Health, Aging and Body Composition Study.


METHODS
Black and white men (n = 482) and women (n = 516) aged 73.1 ± 2.7 and initially free of disability.


METHODS
A group-based trajectory model was used to determine BMI trajectories, the path a person's BMI followed over 9 years. Lean mass, gait speed, grip strength, and knee extension strength were assessed at baseline and after 9 years, and relative changes were calculated. Multivariable linear regression was used to determine associations between trajectories and relative change in lean mass and physical function.


RESULTS
Four BMI trajectories were identified for men and four for women. Although all demonstrated a decline in BMI, the rate of decline differed according to trajectory for women only. Men in Trajectory 4 (mean BMI at baseline 33.9 ± 2.3 kg/m(2) ) declined more than those in Trajectory 1 (mean BMI at baseline 22.9 ± 1.6 kg/m(2) ) in gait speed (-9.91%, 95% confidence interval (CI) = -15.15% to -4.67%) and leg strength (-8.63%, 95% CI = -15.62% to -1.64%). Women in Trajectory 4 (mean BMI at baseline 34.9 ± 3.0 kg/m(2) ) had greater losses than those in Trajectory 1 (mean BMI at baseline 20.5 ± 1.6 kg/m(2) ) in lean mass in the arms (-3.19%, 95% CI = -6.16% to -0.23%). No other associations were observed.


CONCLUSIONS
Obese men had the highest risk of decline in physical function despite similar weight loss between trajectories, whereas overweight and obese women who lost the most weight had the greatest risk of lean mass loss. The weight at which a person enters old age is informative for predicting loss in lean mass and physical function, illustrating the importance of monitoring weight.
Laboratory of Epidemiology and Population Science, Intramural Research Program, National Institute on Aging, Bethesda, Maryland.|Department of Health Sciences and the EMGO Institute for Health and Care Research, VU University, Amsterdam, the Netherlands.
Ilse
I
Reinders
Laboratory of Epidemiology and Population Science, Intramural Research Program, National Institute on Aging, Bethesda, Maryland.
Rachel A
RA
Murphy
Laboratory of Epidemiology and Population Science, Intramural Research Program, National Institute on Aging, Bethesda, Maryland.|Epidemiology Group, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, UK.
Kathryn R
KR
Martin
Department of Health Sciences and the EMGO Institute for Health and Care Research, VU University, Amsterdam, the Netherlands.
Ingeborg A
IA
Brouwer
Department of Health Sciences and the EMGO Institute for Health and Care Research, VU University, Amsterdam, the Netherlands.|Department of Nutrition and Dietetics, Internal Medicine, VU University Medical Center, Amsterdam, the Netherlands.
Marjolein
M
Visser
Department of Physical Therapy, University of Delaware, Newark, Delaware.
Daniel K
DK
White
Department of Epidemiology, Center for Aging and Population Health, University of Pittsburgh, Pittsburgh, Pennsylvania.
Anne B
AB
Newman
Sticht Center on Aging, Section on Gerontology and Geriatric Medicine, Department of Internal Medicine, School of Medicine, Wake Forest University, Winston-Salem, North Carolina.
Denise K
DK
Houston
Division of General Internal Medicine, University of California at San Francisco, San Francisco, California.
Alka M
AM
Kanaya
Heinz College, Carnegie Mellon University, Pittsburgh, Pennsylvania.
Daniel S
DS
Nagin
Laboratory of Epidemiology and Population Science, Intramural Research Program, National Institute on Aging, Bethesda, Maryland.
Tamara B
TB
Harris
D000368:Aged; D000375:Aging / Q000502:physiology*; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment; D006304:Health Status; D006801:Humans; D015994:Incidence; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D011446:Prospective Studies; D012307:Risk Factors; D013851:Thinness / Q000453:epidemiology* / Q000209:etiology; D013997:Time Factors; D014481:United States; D015431:Weight Loss / Q000502:physiology*
aging; body mass index; lean mass; physical function; trajectories