Can Physical Activity Attenuate Aging- related Weight Loss in Older People? The Yale Health and Aging Study, James Dziura, Carlos Mendes de Leon, Stanislav Kasl, and Loretta DiPietro

Background Body weight increases through middle-age, but starts to decline during older age; This decline occurs primarily as a result of loss in lean tissue (sarcopenea); Sarcopenea is a primary condition for loss of physical and metabolic reserve in aging; Disuse has been identified as a significant factor in lean tissue loss, since changes in body composition are mirrored by a gradual decline in physical activity in older age.

Problem Longitudinal studies of physical activity and weight change have not been performed in older populations, among whom weight loss is a more important problem than weight gain and among whom the relation between physical activity and weight loss is influenced heavily by chronic disease and loss of mobility.

Purpose The purpose of this analysis was to determine, longitudinally, the trajectory of weight loss with age and the relation between physical activity and body weight change in a cohort of people aged 65 years and older.

Hypotheses We hypothesized that: 1) body weight would decline over the follow-up; and 2) physical activity would play an important role in minimizing weight loss over time.

Methods Subjects Older residents (≥65 y) of New Haven, CT enrolled in the Yale Health and Aging Project – one of the funded sites of the Established Populations for the Epidemiologic Study of the Elderly (EPESE).

Methods Subjects The New Haven EPESE cohort was a cluster sample stratified by three different housing types for older people: 1) public housing; 2) private housing; and 3) housing in the general community. Of the 3,337 eligible residents contacted, 2,812 (82%) enrolled in the study at baseline in 1982.

Exclusion Hierarchy Interested subjects (N=2,812)

Methods Body weight Current body weight was self-reported at each yearly interview from 1982 to 1990 and then again in Each subject could have as many as 10 weight assessments over the 12-year follow-up.

Methods Physical Activity Respondents were asked to report the frequency of participation within the past month for four general types of activities: 1) walking; 2) gardening/housework; 3) physical exercise; and 4) active sports or swimming. Responses of never (coded as 0), sometimes (coded as 1) or often (coded as 2) were summed over the four activities for each respondent to create a total activity score (TAS) that ranged from 0 to 8, with higher scores indicating higher levels of baseline activity.

Covariables at Baseline Age (date of initial interview - reported birth date); Height (inches); Race (white/non-white); Education (number of years); Chronic conditions (reported number of physician-diagnoses of heart disease, cancer, stroke, diabetes, liver disease, or hypertension); Smoking (smoker/non-smoker); Functional Ability Score (ADLs, IADLs); Mobility Score (reported ability (yes/no) to climb stairs, do house work, and walk ½ mile)

Statistical Analysis Univariate statistics (Χ±SD; %); Multivariable random effects modeling (repeated body weight assessments over a maximum of 10 times ( ) regressed on physical activity, while adjusting for covariables). This modeling accounts for between-subject variation in baseline body weight (intercept) and change in body weight with aging (slope; as indicated by follow-up time variable).

Table 1. Cross-sectional distribution of mean (±sd) body weight at each year of follow-up among those who survived and those who did not survive to the next interview year. YEARN Body weight (lbs)N Body weight (lbs) ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±24 Survived to next interview yearDid not survive to next interview year

Table 2. – Baseline characteristics of the study sample by survival status over the follow-up, VariableSurvivors (N=905) Non-survivors (N=1395) Age (yrs)71±576±7 * Sex (% Female)69%51% # Race (% White)78%81% Education (yrs)10±49±4 * Disability score0.13± ±1.30 * Mobility score0.39± ±1.06 * Chronic conditions1±0.771±0.92 Smokers (%)18%23% Height (in)64.3± ±3.71 Weight (lbs)155±30153±32 Total Physical Activity Score 2.62± ±2.19 * * p<0.001 based on t-test for independent samples; # p<0.01 based on chi-square test.

Figure 2. - Predicted weight loss (95% confidence bands) over the first 8 years based on random effects modeling*: Survivors Non-survivors YEAR Body weight (lbs) * Model adjusted for age, sex, housing strata, and interaction of each with time.

Table 3. - Simple effects of physical activity on weight loss: VariableEstimate95% CIEstimate95% CIEstimate95% CI Total Activity Score Total Activity Score * Time , , , , , , 0.31 Based on random effects modeling adjusted for time and time 2. Regression estimates for TAS*Time interaction represent the change in the rate (per year) of weight loss per unit change in the study variable. Non-survivors (n=1,395) Combined (N=2,300)Survivors (n=905)

Table 4. Parameter Estimates* from the Random Effects Model Determining the Effects of Physical Activity on Aging-Related Weight Change. VariableParameter estimate 95% CIParameter estimate 95% CIParameter estimate 95% CI Baseline Age , , , Time , , , Time , , , Age * Time , , , Chronic condition , , , 7.38 Chronic condition * Time , , , 0.72 TAS , , , 0.87 TAS * Time , , , 0.37 TAS*Chronic condition , , 1.43 TAS*Chronic condition*Time , , 0.12 Mobility , , , 0.14 Mobility*Time , , , 0.84 Smoking Smoke * Time , , , , , , 0.97 Combined (N=2,300) Survivors (n=905) Non-survivors (n=1,395) *also adjusted for sex, race, education, height, functional disability score, and housing.

Fig. 3 - Parameter Estimates (95% CI)* from the Fully-Adjusted Random Effects Model Determining the Effects of Physical Activity Score on Attenuation of Weight Loss by Survival and Chronic Disease Status. Combined (N=2300) Survivors with no chronic disease (n=350) Survivors with chronic disease (n=555) Non-survivors with no chronic disease (n=422) Non-survivors with chronic disease (n=973) Attenuation of weight loss (lbs/year) 0.09 (0.02, 0.15) (-0.11, 0.07) 0.09 (0.00, 0.17) 0.06 (-0.12, 0.25) 0.15 (0.00, 0.30)

Summary T he oldest people started off the follow-up period weighing less than their younger counterparts; T he magnitude of the inverse relation between age and body weight was greater among nonsurvivors compared with survivors;

Summary W e observed a curvilinear rate of weight loss with aging that varied by survival status and by chronic disease. T he ability of physical activity to attenuate aging-related weight loss was observed only among those with chronic disease, and was most pronounced among those with chronic disease who did not survive the follow-up period.

Conclusion I f we were to consider weight loss a somatic indicator of frailty in older people, it appears as though even among older people afflicted with chronic conditions that contribute to frailty, an active lifestyle can attenuate the rate of failure, thereby maintaining some quality of health and function in older age.