Kidney International, Vol. 56 (1999), pp. 244–252
`
`Total body water data for white adults 18 to 64 years of age:
`The Fels Longitudinal Study
`
`W. CAMERON CHUMLEA, SHUMEI S. GUO, CHRISTINE M. ZELLER, NICHOLAS V. REO,
`and ROGER M. SIERVOGEL
`
`Department of Community Health and Department of Biochemistry and Molecular Biology, Wright State University
`School of Medicine, Dayton, Ohio, USA
`
`Total body water data for white adults 18 to 64 years of age:
`The Fels Longitudinal Study.
`Background. Total body water (TBW) volume is reported
`to decrease with age, but much of the published data are 20
`to almost 50 years old and are cross-sectional. Proper interpre-
`tation of clinical levels of TBW and trends with age necessitates
`the availability of current longitudinal data from healthy indi-
`viduals.
`Methods. Mixed longitudinal data for TBW of 274 white
`men and 292 white women (18 to 64 years of age) in the Fels
`Longitudinal Study were collected on a regular schedule over
`a recent eight-year period. The concentration of deuterium
`was measured by deuterium nuclear magnetic resonance spec-
`troscopy. Body composition estimates were made with dual-
`energy x-ray absorptiometry, and random effect models were
`used to determine the patterns of change over time with and
`without covariates.
`Results. The mean TBW data for the Fels men are either
`similar to or approximately 2 to as much as 6 liters greater
`than that reported by most other investigators 20 to 50 years
`ago. For Fels women, the mean TBW ranges from approxi-
`mately 2 to as much as 5 liters less than that reported previously.
`These comparisons with much earlier studies reflect cohort
`effects and the secular changes in overall body size that have
`occurred during the past 60 to 70 years. These findings are
`reinforced by the fact that some early data sets included individ-
`uals born almost 140 years ago. After adjusting for the covariate
`effects of total body fat (TBF) and fat-free mass (FFM) with
`age, there were no significant age or age-squared effects on
`TBW in the men. In the women, after adjusting for the covari-
`ate associations of TBF and FFM with age, there was a small,
`but significant, negative linear association of TBW with age.
`In the men and women, the mean ratio of TBW to weight
`declined with age as a function of an increase in body fatness
`and more so for the men than the women.
`Conclusion. The findings from these mixed longitudinal data
`indicate that TBW volume, on average, maintains a reasonable
`degree of stability in men and women through a large portion
`
`Key words: intracellular water, extracellular water, body weight, fat,
`obesity.
`
`Received for publication November 6, 1998
`and in revised form January 29, 1999
`Accepted for publication February 10, 1999
`© 1999 by the International Society of Nephrology
`
`of adulthood. These TBW data are recommended as current
`reference data for healthy adults.
`
`Water is the major chemical component of the body
`and the essential medium of the body’s internal environ-
`ment [1–3]. Approximately 65% of total body water
`(TBW) is intracellular (ICW) with an 35% extracellular
`water (ECW) in the proverbial 70 kg person. TBW vol-
`ume in a healthy, weight (WT)-stable adult reportedly
`fluctuates approximately ⫾5% daily because of ongoing
`physiological processes and the consumption of food and
`drink [1]. Differences in climate, salt intake, level of
`physical activity, and cultural habits are additional fac-
`tors that affect the interindividual variance of levels of
`TBW, along with numerous pharmacological agents,
`most commonly caffeine [4, 5]. TBW volume is further
`affected by disease, especially renal insufficiency, along
`with diabetes, liver disease, cancer, and heart disease [6].
`The proper interpretation of clinical levels of TBW as a
`function of disease necessitates the availability of timely
`corresponding comparative data from healthy individu-
`als [7, 8].
`Healthy adult men, on average, consistently have
`larger amounts of TBW than women as a function of
`their larger size and muscle mass [9, 10]. Mean values
`for TBW have been reported to range from approxi-
`mately 35 to 45 liters in men and approximately 25 to
`33 liters in women, depending on age [9–14]. The level
`of TBW reportedly starts to decrease around middle
`age in men and women and is rapid in women after
`approximately 60 years of age [3, 15, 16]. The average
`decline between 20 and 80 years of age is reported to
`be about 4 liters in men and 6 liters in women [9–11, 14,
`17, 18]. A decline in TBW with age could be due to a
`reduction in the volume of ICW or the body cell mass
`and/or a fall in the volume of ECW [3, 16]. The latter
`is thought to occur with the aging process by some inves-
`tigators [19, 20] but not others [11, 15].
`
`244
`
`1
`
`Hopewell EX1082
`Hopewell v. Merck
`IPR2023-00481
`
`

`

`Chumlea et al: The Fels Longitudinal Study
`
`245
`
`Total body water comprises approximately 50 to 60% Longitudinal Study is an ongoing study of the growth,
`of adult body WT with a range from 45 to 75% [19, 21,
`development, body composition, and aging of white per-
`sons born between 1929 and the present, approximately
`22]. The breadth of this range is due to sex and age
`differences and levels of leanness or fatness; that is, if
`75% of whom live in Ohio or contiguous states. Sched-
`uled visits for participants were at two- to five-year inter-
`there is more muscle, then there is proportionately more
`water, or if there is more fat, then there is proportion-
`vals. In this mixed serial data set, there were one to four
`visits per participant, with a maximum of six years of
`ately less water [23, 24]. The ratio of TBW to weight
`(TBW/weight) also decreases in adults with age [19].
`follow-up. This produced a total of 504 visits for the
`This decrease is a function of either a decline in TBW men and 553 visits for the women. All procedures were
`volume with aging or as a gain in weight and fatness that
`approved by the Institutional Review Board of Wright
`State University (Dayton, OH, USA).
`also occurs with increased age in many adults today [10,
`14, 19, 25]. Body fatness is considered the most important
`Stature and weight were collected according to stan-
`dardized procedures at each visit [28]. To measure TBW,
`factor, except for disease, in describing TBW content
`among individuals at any point in life [6]. However, the
`each participant provided a baseline saliva sample to
`determine the natural abundance of deuterium and then
`extent to which variations in levels of fatness among
`received 15 g of deuterium oxide (D2O, 99.8%) in 150
`individuals affects TBW has not been presented. The
`cm3 of water. A second saliva sample was taken at least
`effect of the level of fatness on the change in TBW with
`age is an important factor in interpreting the clinical
`two hours after the deuterium dose. The concentration
`of the deuterium dose in the specimen samples was mea-
`management of TBW [16].
`This article reports the status of TBW in normal adults
`sured by deuterium nuclear magnetic resonance (NMR)
`spectroscopy and was corrected for natural abundance
`and its relationship to increasing age and levels of body
`fatness. Most reported reference values for TBW are
`and isotope exchange [29]. These procedures have been
`reported in detail previously [30].
`now several, if not many decades old, but their results
`Body composition estimates were made with dual en-
`are generally accepted and are still widely quoted. It is
`ergy x-ray absorptiometry (DXA) using a Lunar DPX娃
`reasonable to consider how this earlier TBW literature
`machine with version 3.6z software (Lunar Radiation
`compares with more current data. Also, the reported
`Corp., Madison, WI, USA). Fat-free mass (FFM) in kilo-
`age and sex trends in TBW are from analyses of cross-
`grams was calculated as the sum of whole body lean
`sectional data. Such analyses cannot demonstrate an ef-
`tissue (g) and whole body bone mineral mass (g) divided
`fect of age because of the independence of each subject
`by 1000. The total tissue mass (g) for the whole body
`and potential cohort effects. In order to demonstrate a
`was calculated as the sum of the total soft tissue and
`real change with age requires the validity that comes
`bone mineral mass values. Body composition values for
`from a longitudinal study of individuals followed over
`the percentage of body fat (%BF) were calculated as
`time [3]. This article looks at a set of mixed longitudinal
`whole body fat tissue (g) or the total body fat (TBF)
`data for TBW in white adults 18 to 64 years of age
`divided by total tissue mass (g).
`collected on a regular schedule over a recent eight-year
`period. These data allow the determination of patterns
`of intraindividual and interindividual changes in TBW
`relative to concurrent measures of body composition
`through the use of improved statistical models. This
`study also examines the relationship between levels of
`fatness and TBW. In light of the increased prevalence
`of obesity in the U.S. population over the past several
`decades [26], this increased fatness among adults and its
`effects on TBW values need to be considered. A better
`understanding of the status of TBW in normal adults
`living today should provide a useful comparison for clini-
`cal interpretations of TBW in cases of disease.
`
`Statistical methods
`Cross-sectional analysis. This set of mixed serial data
`was arranged into a cross-sectional format of five, 10-
`year age groups starting at 20 years of age in order to
`compare it with existing published data. An individual
`participant’s data were represented only once within
`each age group, but it could be represented in two adja-
`cent age groups. Descriptive statistics, including means
`and standard deviation, were computed for stature,
`weight, body mass index (BMI), and TBW for each par-
`ticipant. These calculations were also conducted for
`those participants who had concurrent measures of FFM,
`TBF, and %BF from DXA.
`Longitudinal analysis. Using the complete mixed lon-
`gitudinal data set, means and standard deviations for
`TBW and TBW/WT were computed for age groups sepa-
`rated into two-year intervals from 18 through 64 years
`of age for men and women separately. The means and
`one sd were plotted by the midpoint of the age intervals
`
`METHODS
`This study sample included 274 Caucasian men and
`292 Caucasian women between 18 and 64 years of age.
`These healthy participants were observed at regularly
`scheduled visits as long-term participants in the Fels Lon-
`gitudinal Study [27] between 1989 and 1996. The Fels
`
`2
`
`

`

`246
`
`Chumlea et al: The Fels Longitudinal Study
`
`Table 1. Means and standard deviations for 10-year age groups using one observation per participant in each age group
`
`Age groups
`40–49 years
`
`72
`43.94 ⫾ 6.26
`84.39 ⫾ 11.88
`181.8 ⫾ 8.61
`25.57 ⫾ 3.37
`57
`22.90 ⫾ 8.75
`60.93 ⫾ 7.25
`26.80 ⫾ 8.07
`
`50–59 years
`
`60⫹ years
`
`57
`43.83 ⫾ 6.99
`86.42 ⫾ 13.93
`177.7 ⫾ 5.84
`27.33 ⫾ 4.09
`40
`25.30 ⫾ 9.40
`60.33 ⫾ 7.05
`28.76 ⫾ 8.09
`
`30
`42.87 ⫾ 5.97
`93.06 ⫾ 15.37
`177.2 ⫾ 6.03
`29.78 ⫾ 5.68
`24
`28.08 ⫾ 9.34
`60.22 ⫾ 4.76
`31.19 ⫾ 7.00
`
`Units
`
`20–29 years
`
`30–39 years
`
`90
`41.90 ⫾ 6.69
`74.54 ⫾ 13.00
`179.5 ⫾ 7.20
`23.08 ⫾ 3.60
`69
`14.90 ⫾ 6.87
`59.44 ⫾ 7.74
`19.50 ⫾ 7.24
`
`57
`43.30 ⫾ 6.13
`81.41 ⫾ 13.85
`179.8 ⫾ 7.80
`24.18 ⫾ 4.01
`39
`22.12 ⫾ 7.29
`60.30 ⫾ 8.24
`25.49 ⫾ 6.60
`
`liters
`kgs
`cm
`kg/m2
`
`kgs
`kgs
`%
`
`liters
`kgs
`cm
`kg/m2
`
`Variables
`Men
`N
`TBW
`Weight
`Stature
`BMI
`N*
`TBF
`FFM
`PBF
`Women
`29
`69
`88
`80
`85
`N
`27.80 ⫾ 3.56
`29.99 ⫾ 4.15
`30.72 ⫾ 5.17
`31.00 ⫾ 4.54
`30.70 ⫾ 4.91
`TBW
`64.87 ⫾ 11.72
`70.29 ⫾ 13.14
`69.68 ⫾ 16.27
`67.13 ⫾ 13.02
`65.31 ⫾ 14.83
`Weight
`163.2 ⫾ 6.65
`165.5 ⫾ 5.58
`165.4 ⫾ 5.75
`166.1 ⫾ 5.94
`166.2 ⫾ 7.00
`Stature
`24.35 ⫾ 4.26
`25.65 ⫾ 4.46
`25.46 ⫾ 5.69
`24.28 ⫾ 4.30
`23.62 ⫾ 5.16
`BMI
`27
`61
`65
`62
`59
`N*
`25.88 ⫾ 8.77
`29.52 ⫾ 9.99
`27.60 ⫾ 11.22
`25.00 ⫾ 9.76
`23.34 ⫾ 11.49
`kgs
`TBF
`38.26 ⫾ 4.76
`41.13 ⫾ 5.04
`41.67 ⫾ 5.32
`41.99 ⫾ 5.48
`42.20 ⫾ 5.21
`kgs
`FFM
`39.40 ⫾ 7.70
`40.76 ⫾ 7.53
`38.57 ⫾ 8.18
`36.23 ⫾ 8.70
`33.97 ⫾ 9.23
`%
`PBF
`N* is the sample size for those with DXA data. Data are mean ⫾ sd. Abbreviations are: TBW, total body water; BMI, body mass index; TBF, total body fat;
`FFM, fat-free mass; PBF, percent body fat.
`
`for TBW and TBW/weight. In addition, the relationships
`with age in the sample were explored in these data.
`Random effect models were used to determine the pat-
`terns of change over time in TBW. The parameters in the
`models characterized individual differences. This type of
`statistical model analyzes the complete set of serial and
`cross-sectional data and handles the occurrence of miss-
`ing values and measurements taken at varying time inter-
`vals. Missing values are estimated by maximum likeli-
`hood procedures assuming that the pattern of change
`for an individual follows a pattern similar to the group.
`Random effect models also allow for the inclusion of
`covariates such as sex and amount of body fat [31].
`
`RESULTS
`Descriptive data
`Means and standard deviations for the variables are
`presented cross-sectionally in Table 1 for men and
`women by 10-year age groups. Within each age group,
`the men were significantly taller and heavier and had
`more TBW and FFM and less %BF than the women.
`At the youngest age group, the women had more TBF
`than the men, whereas the men had significantly larger
`BMIs than the women at the oldest two age groups.
`Mean TBW from one age group to the next ranged from
`approximately 42 to 44 liters in the men and 28 to 31
`liters in the women.
`
`Total body weight comparative data
`We compared the mean TBW volumes of these Fels
`men and women to corresponding mean values selected
`
`from reports by other investigators as early as the 1950s.
`This was a visual comparison because statistical methods
`were not always appropriate (Table 2). In some in-
`stances, distribution statistics were not presented. In oth-
`ers, only tabular lists were presented, and for some, there
`were differences in methodology or age ranges that were
`not comparable. In Table 2, reported means for three
`studies cover a 20-year rather than a 10-year age range.
`In the youngest age group, the mean TBW value for
`Fels men tended to be several liters smaller than that
`reported by Cohn et al [11], Edelman et al [8], and
`Watson et al [32], but larger than those values reported
`by Norris, Lundy, and Shock [13], Lesser and Markofsky
`[10], or Steele et al [14]. For the 30 to 39 year age group,
`the mean TBW values of the Fels men were again smaller
`than those reported by Watson et al [32] and Edelman
`et al [8], but larger than those of the other investigators.
`At the remaining age groupings, the mean TBW values
`of the Fels men were several liters larger than means
`reported by all the other investigators, except for the
`40- to 49- and 50- to 59-year groupings for the data of
`Cohn et al [11] and the 60- to 69-year grouping for the
`data of Baumgartner et al [33]. In comparisons among
`the women, the Fels women had mean TBW volumes
`consistently smaller than those reported by Watson et
`al [32], Cohn et al [11], and Baumgartner et al [33] at
`all age groups. These four data sets (Fels, Watson, Cohn,
`and Baumgartner) had mean TBW values consistently
`larger than those reported for 20-year age ranges by
`Edelman et al [8], Steele et al [14], and Lesser and Mar-
`kofsky [10] at all comparable age groups or groupings
`except the oldest. At the youngest and most contempora-
`
`3
`
`

`

`Chumlea et al: The Fels Longitudinal Study
`
`247
`
`Table 2. Reported mean values for total body water (TBW in liters) for white adults by age and sex
`
`Fels 1999
`TBW
`
`N
`
`Norris 1963
`Cohn 1980
`Watson 1980
`TBW N
`TBW N
`TBW
`
`N
`
`Baumgartner
`1995
`TBW
`
`N
`
`Edelman
`Lesser 1979
`Steele 1950
`1952
`TBW N
`TBW N
`TBW
`
`N
`
`12
`
`41.1
`
`10
`
`38.1
`
`10
`
`31.9
`
`13
`
`29.5
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`36.6
`
`33.4
`
`29.5
`
`28.0
`
`26.4
`
`25.0
`
`12
`
`22
`
`14
`
`18
`
`4
`
`5
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`34
`
`10
`
`6
`
`18
`
`6
`
`5
`
`44.1
`
`43.8
`
`38.1
`
`29.4
`
`28.3
`
`28.4
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`⎫⎬⎭
`
`4
`23
`35
`30
`26
`21
`4
`
`39.4
`41.7
`41.6
`39.9
`41.7
`38.6
`39.1
`
`46.9
`41.0
`44.7
`45.2
`41.0
`40.3
`
`32.2
`33.1
`31.5
`32.0
`28.5
`26.6
`
`17
`78
`31
`
`50
`80
`51
`
`43.0
`42.4
`40.4
`
`30.9
`29.6
`28.2
`
`Gender
`years
`Men
`20–29 years
`30–39 years
`40–49 years
`50–59 years
`60–69 years
`70–79 years
`80–89 years
`Women
`20–29 years
`30–39 years
`40–49 years
`50–59 years
`60–69 years
`70–79 years
`80–89 years
`} ⫽ spans pairs of age ranges, for example, 20–29 and 30–39.
`
`90
`57
`72
`57
`30
`
`85
`80
`88
`69
`29
`
`41.9
`43.3
`43.9
`43.8
`42.9
`
`30.7
`31.0
`30.7
`30.0
`27.8
`
`171
`93
`59
`68
`33
`23
`
`100
`48
`37
`43
`19
`5
`
`43.3
`44.1
`41.2
`39.7
`36.7
`33.2
`
`32.2
`31.4
`32.1
`33.2
`32.6
`25.8
`
`24
`10
`10
`10
`10
`9
`
`10
`10
`10
`10
`14
`8
`
`neous matches, the means for TBW in the Fels men and
`women were less than that reported by studies. At older
`age groups, the mean TBW in Fels men was larger than
`in earlier studies, but the mean TBW in Fels women was
`smaller than reported in earlier studies.
`
`Total body water relationships with age
`The data sets of the earlier cross-sectional studies ex-
`cept Cohn et al all demonstrate a sequential decline in
`mean TBW volumes with each older age group [11]. This
`age trend only appeared in the Fels men at the 60-to-69
`year age group and in the men in the study of Cohn et
`al at the 60-to-69 and 70-to-79 year age groups [11]. This
`trend also appears across the 30 year age range in the
`data of Baumgartner et al, but these data start at age 60
`years [33]. The mean TBW volumes of the Fels women
`showed a decline with age starting at the 50-to-59 year
`age group. The only decline for women with age noted
`by others started at the 60-to-69 year age group in the
`data of Cohn et al and Baumgartner et al and at the 70-
`to-79 year age group [11] in the data of Steele et al and
`Watson et al [14, 32].
`To determine more clearly the relationship of TBW
`with age in these data, the means and one standard
`deviation for TBW at two-year age intervals from 18 to
`64 years are presented for the men and women separately
`in Figure 1. To test for age-related changes in TBW, a
`random effects model was applied to these mixed longi-
`tudinal data without any adjustments for possible covari-
`ates (Table 3). TBW was not significantly associated with
`age or age squared (age2) in the men from 18 to 64 years
`of age. However, in the women from 18 to 64 years of
`age, there was a significant (P ⬍ 0.05) linear (age) and
`curvilinear or quadratic relationship of TBW with age2
`(Table 3).
`
`Further age relationships with stature, weight and lev-
`els of FFM, TBF and %BF also were determined with
`a random effect model (Table 3). Within these mixed
`serial data, there were significant, positive linear associa-
`tions of age separately with weight, TBF, and %BF
`among the men and women. There were no significant
`relationships of age with stature in the men or in the
`women, but a negative relationship of FFM and age in
`the women was marginally significant (P ⬍ 0.051).
`To clarify these age relationships further, a random
`effects model for TBW including age, age2, and TBF and
`FFM as independent variables was analyzed (Tables 3
`and 4). After taking into consideration the interrelation-
`ships of TBF, FFM, and age within the model, again
`there were no significant age or age2 effects on TBW in
`the men. In the women, after adjusting for the covariate
`associations of TBF, FFM, and age, there remained a
`small but significant negative linear association of TBW
`with age, but no significant quadratic relationship inde-
`pendent of TBF and FFM (Table 4). In the women,
`higher values for both TBF and FFM were associated
`with increased levels of TBW. In the men, higher values
`for FFM but not TBF were associated with increased
`levels of TBW.
`
`Total body water and body composition
`Total body water/weight had a significant linear de-
`cline (P ⬍ 0.05) with age in both the men and women
`(Table 3), but the decrease was greater in the men than
`the women. In the men, the mean TBW/weight at an
`age declined from approximately 58% at age 18 years
`to approximately 46% at age 64 years (Fig. 2). In the
`women, the decline with age was not as steep as in the
`men, with the mean TBW/weight decreasing from 48%
`at age 18 years to approximately 43% at age 64 years.
`
`4
`
`

`

`248
`
`Chumlea et al: The Fels Longitudinal Study
`
`Fig. 1. Means and 1 SD for total body water
`(TBW) for males (䊏) and females (䊉) at two-
`year age intervals.
`
`Table 3. Regressions of study variables on age using the
`random effects model
`
`Intercept
`
`Age
`
`Age2
`
`37.6
`32.0
`70.0
`179.9
`63.0
`60.7
`3.3
`7.7
`
`Men
`TBW liter
`TBW/WT %
`TBW/FFM %
`Stature cm
`Weight kg
`FFM kg
`TBF kg
`%BF %
`Women
`22.5
`TBW liter
`52.0
`TBW/WT %
`72.0
`TBS/FFM %
`165.9
`Stature cm
`54.1
`Weight kg
`45.8
`FFM kg
`13.4
`TBF kg
`23.1
`%BF %
`Abbreviations are as in Table 1.
`a P ⬍ 0.05
`
`—
`⫺0.22a
`—
`—
`0.49a
`0.04
`0.42a
`0.39a
`
`0.46a
`⫺0.15a
`—
`—
`0.35a
`⫺0.051a
`0.26a
`0.27a
`
`—
`—
`—
`—
`—
`—
`—
`—
`
`⫺0.01a
`—
`—
`—
`—
`—
`—
`—
`
`in FFM in both men and women (mean of approximately
`0.68) did not change with age. This finding was not unex-
`pected because there was little or no change with age in
`TBW or FFM in the men. In the women, because TBW
`and FFM were both declining slowly with age, then the
`ratio should remain relatively stable. These findings were
`confirmed with the random effects models, which showed
`no significant effects of age or age2 on FFM for men and
`women.
`In both the men and the women, TBF and %BF in-
`creased significantly with age. This increase in body fat-
`ness indicates that the decline in TBW/weight with age
`is, in great part, a function of an increase in body fatness
`and more so for the men than among the women. To
`clarify this relationship, a multiple regression of TBW/
`weight at an age on TBF and on %BF was conducted
`after removing associations with age among the vari-
`ables. In the men and women, 40 to 45% and 44 to
`56% of the variance, respectively, in TBW/weight was
`inversely related to the level of TBF or %BF, respec-
`tively; that is, the higher the level of fatness in an individ-
`ual, the lower the TBW/weight. Thus, the interindividual
`variance in TBW/weight is, in large part, affected by the
`level of individual fatness rather than the level of TBW
`regardless of sex or age.
`
`Because TBW did not change with age in the men,
`the decrease in TBW/weight in the men is due solely to
`an increase in weight over the age period. In the women,
`TBW decreased slowly with age, whereas weight in-
`creased with age. This small loss of TBW in the women
`implies a loss of FFM with age, which was marginally
`DISCUSSION
`significant. However, an increase in weight in both the
`The volume of TBW in this study was measured in
`men and women signals an increase in fatness. To deter-
`vivo by the dilution method using deuterium labeling and
`mine the extent to which the relationships of TBW and
`deuterium NMR [29]. Deuterium is the most commonly
`weight with age were associated with concurrent changes
`used solute, and its concentration can be quantitated
`in body composition, the relationship of TBW to FFM,
`TBF, and %BF were explored. The percentage of TBW accurately in body fluid specimens by mass spectrometry,
`
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`Chumlea et al: The Fels Longitudinal Study
`
`249
`
`Table 4. Model results of regression of target age on total body water with fat and fat-free mass measures from random effects model
`
`Intercept
`
`Age
`
`Age2
`Estimate se
`
`0.002 (0.001)
`
`⫺0.001 (0.001)
`
`TBF
`
`FFM
`
`0.07b (0.03)
`0.06 (0.03)
`0.05 (0.03)
`
`0.10b (0.02)
`0.10b (0.02)
`0.08b (0.02)
`
`0.67b (0.03)
`0.66b (0.03)
`0.67b (0.03)
`
`0.66b (0.03)
`0.67b (0.03)
`0.67b (0.03)
`
`3.45 (2.64)
`1.40 (2.12)
`0.56 (2.02)
`
`⫺2 ll
`Men
`1278.2
`1279.8
`1281.4a
`Women
`⫺0.12 (1.58)
`1430.5
`0.65 (1.33)
`1431.3a
`⫺0.85 (1.22)
`1438.3
`Abbreviation: ⫺2 ll is the ⫺2 log likelihood value.
`a Selected model based upon ⫺2 ll and significant regression parameters
`b P ⬍ 0.05
`
`⫺0.17 (0.11)
`⫺0.02 (0.02)
`
`0.03 (0.06)
`⫺0.03b (0.01)
`
`Fig. 2. Means and 1 SD for TBW/weight for
`males (䊏) and females (䊉) at two-year age in-
`tervals.
`
`infrared spectrometry, or NMR [29]. Other solutes have
`been used in the past, and comparative studies have
`reported a high level of agreement among subjects, sol-
`utes used, specimens, and laboratory methods [14, 21,
`24, 29].
`
`Total body water comparative data
`There are no currently available national reference
`data for TBW. This mixed longitudinal data set is one
`of the largest used to report TBW. Except at the youngest
`two age groups for men and the youngest age group for
`women, the number of participants per 10-year age group
`is similar or two to eight times as large as that reported
`by other previous studies (Table 2). Except for the data
`sets of Cohn et al [11], Baumgartner et al [33], Norris,
`Lundy, and Shock [13], and Watson et al [32], the sample
`
`sizes of the other reported studies are very small, and
`the findings could be considered possibly anecdotal. The
`data set of Watson is a composite of up to 30 separate
`independent studies. This data set was created with some
`regard to sample, design, or methodological differences,
`but the representative quality of the findings reported
`by Watson et al is questionable [32]. Also, these data
`sets included individuals with diagnosed clinical condi-
`tions [12].
`At all of the age groupings, the means for TBW among
`the data from Fels, those of Cohn et al [7] up to 59 years,
`and those of Baumgartner et al [33] from 60 to 79 years
`of age and the data of Norris, Lundy, and Shock [13]
`and Watson et al [32] from 20 to 49 years of age are
`similar, ranging from about 41 to 44 liters in men. From
`20 to 59 years of age, mean TBW in the women from
`
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`250
`
`Chumlea et al: The Fels Longitudinal Study
`
`the studies of Fels, Watson et al [32], and Cohn et al [7]
`are almost reversed at the older ages where the means
`and that of Baumgartner et al [33] at 60 to 69 years of
`for FFM in the Fels men are almost 5 kg greater than
`age are similar ranging from about 31 to 33 liters. The
`those of the older men from the data of Lesser and Mar-
`mean TBW data for the Fels men and that of Baum-
`kofsky [10], but the means for FFM of these older women
`gartner et al [33] at the older age groups is, on average,
`are approximately 3 kg larger than that of the Fels
`approximately 2 to as much as 6 liters greater than that
`women. In comparison with the data from Watson et al,
`reported by all but one of the other studies, 20 to 40
`the means for %BF of the Fels men are 2 to 8% larger
`years ago. The findings for Fels women indicate that, on
`at all age groups, whereas the means for the Fels women
`average and at almost all age groups, the mean TBW are approximately 2 to 6% greater except at the oldest
`ranges from approximately 2 to as much as 5 liters less
`age group [32]. These Fels men and women tend to be
`fatter than the men and women in the earlier studies.
`than that reported previously. Thus, there are distinct
`differences in means for TBW for Fels men and women
`The Fels men were slightly fatter and had more FFM
`than the New Mexico men of Baumgartner et al, but
`when compared with earlier data sets. It should be noted
`that the data of Edelman et al [8], Lesser and Markofsky
`these two groups of women were almost identical [33].
`To some degree, these interstudy differences are due
`[10], and Steele et al [14] are included in the data of
`Watson et al [32].
`to cohort effects that reflect the secular changes in overall
`body size (and fatness) that have occurred during the
`For some of these earlier data sets, comparisons
`among other measured variables and this study are possi-
`past 60 to 70 years [34]. One should also recognize that
`these data of Norris, Lundy, and Shock [13] and of Wat-
`ble. For example, at the youngest age group only, the
`mean statures, weights, and BMI values for the Fels men
`son et al [32] appear to include individuals born during
`the U.S. Civil War or almost 140 years ago. These studies,
`are similar to reported corresponding means by Cohn
`et al [7], Norris, Lundy, and Shock [13], and Watson et
`along with those of Edelman et al [8], Lesser and Markof-
`sky [10], and Steele et al [14], have samples in which
`al [32]. At the older age groups, the mean statures and
`weights of these Fels men are from 1 to 12 cm and from
`approximately 20 to 50% of the subjects were born be-
`fore 1900. The samples of Baumgartner only contain
`3 to 27 kg larger than corresponding means reported by
`Norris, Lundy, and Shock [13] and Watson et al [32]. At
`persons born in the 20th century. Adult averages for
`stature and weight (and strength in men) have increased
`the youngest age groups, the means for stature, WT,
`and BMI for Fels women were similar to corresponding
`with subsequent generations through much of the 20th
`century. In light of this information and the significant
`means reported by Norris, Lundy, and Shock [13] and
`Watson et al [32]. At the youngest age groups, the means
`changes in stature, weight, and body composition with
`each generation, it would appear inappropriate to con-
`for stature, weight, and BMI for Fels women were similar
`to corresponding means reported by Watson et al [32].
`tinue to reference studies that include data from the 19th
`century in the 21st century.
`At the older age groups, these Fels women were, on
`average, 1 to 10 cm taller than the women in the data
`sets of Cohn et al [7] and Watson et al [32]. In comparison
`with the data of Watson et al [32], the mean weights of
`the Fels women at the older age groups were as much
`as 2 to 10 kg less than reported at corresponding age
`groups, but the mean weights of the Fels women were
`similar to those in the data of Cohn et al [7] at the older
`age groups. When compared with the older samples,
`these Fels men are taller and heavier, whereas the Fels
`women are taller but lighter.
`It is also possible to compare mean values for FFM,
`TBF, and %BF from these findings with data reported
`by Norris, Lundy, and Shock [13], Lesser and Markofsky
`[10], Watson et al [32], and Baumgartner et al [33]. In
`the data from Norris, Lundy, and Shock [13], %BF is
`higher, on average, than that of these men, which may
`explain why the means for TBW from Norris, Lundy,
`and Shock are low at these ages. For the data of Lesser
`and Markofsky [10], the mean values for FFM at the
`youngest age groups for men and women are similar to
`those of the Fels men but are approximately 2.5 kg larger
`in comparison with the Fels women. These comparisons
`
`Relationships with age
`In contrast to previously published findings from cross-
`sectional data, these mixed serial data indicate that from
`18 to 64 years of age, TBW volume for men does not
`decline with age. The relationship of TBW with age in
`the women was slightly more complicated during this
`same age period (Table 2). TBW in women had a very
`small but significant negative slope with age independent
`of FFM and TBF (Table 3). This slope was similar to
`that of the men, where it was not significant (Table 3).
`In these mixed serial data, there is little, if any, clear
`decline in TBW volume through much of adulthood.
`TBW volume, on average, maintains a reasonable degree
`of stability in both men and women through a large
`portion of the adult years. Norris, Lundy, and Shock [13]
`and Watson et al [32] are the data sets that report age
`as an independent indicator for TBW for men only. This
`is reported by Baumgartner et al for both men and
`women but at a much older age range [33]. These cross-
`sectional data do not indicate that TBW declines with
`age, as that can only be demonstrated with longitudinal
`
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`

`Chumlea et al: The Fels Longitudinal Study
`
`251
`
`data. Numerous other data sets span large age ranges
`but have very small samples [32]. The presence of an
`age trend in the data of Norris, Lundy, and Shock [13]
`and Watson et al [32] is probably a cohort effect. This
`effect could be accentuated in the data of Watson et al
`by the combination of old data sets and the large number
`of contemporary young subjects at the youngest age
`group [32]. At the oldest age groups, the mean TBW for
`men in the data of Watson et al is 7 to almost 10 liters
`less than that of others (Table 2) [32]. At the same time,
`the absence of an age relationship in several other older
`data sets could be due to sampling or the strong concur-
`rent relationships of TBW with stature and weight that
`can mask an age association [12]. An age effect may
`exist in these data, as indicated by the low values for
`TBW at the oldest age group (Table 1) for men and
`women, but confirmation of this trend will take addi-
`tional longitudinal data and time to demonstrate.
`The nonsignificant decline in TBW in the Fels women
`after age 48 years is possibly indicative of the onset of
`a loss of FFM in these women with the general aging
`process. Forty-nine years is the age at which 50% of U.S.
`women are menopausal [35]. Among the Fels women,
`the average age at menopause is 50 years [31]. There
`was a marginally significant, small negative age effect on
`TBW (and almost for FFM) in these women from 18 to
`64 years, in which the drop from 48 to 64 years of age
`made a significant contribution (Fig. 1