pet Ownership, Social Year Survival Afler Infarction in the Cardiac Suppression bial Erika Friedmann,
POD, and Sue A. Thomas,
Social support and pet ownership, a nonhuman form of social support, have both been associated with increased coronary artery disease survival. The independent effects of t ownership, social support, disease severity, and o tr er psychosocial factors on 1-year survival after acute myocardial infarction are examined prospectively. The Cardiac Arrhythmia Suppression Trial provided physiologic data on a group of posk-rnyocardial infarction patients with asymptomatic ventricular arrhythmias. An ancillary stu provided psychosocial data, including pet owners t ip, social support, recent life events, future life events, anxiety, de ression, coronary prone behavior, and expression cf anger. Subjects (n = 424) were mndomly selected from patients attending participating Cardiac Arrhythmia Suppression Trial sites and completed baseline psychosocial questionnaires. One year survival data were ob-
RN, PhD
eO.05); amount of social support is also an independent predictor of survival (p = 0.065). Both pet ownership and social support are significant predictors of survival, independent of the effects of the other psychosocial factors and physio ic status. These data confirm and extend previous fin 9 ings relating pet ownership and social sup rt to survival among patients with coronary artery dPisease. (AmJCardiol 1995;76:1213-1217)
upport from nonhuman companions has been linked METHODS to coronary artery disease patient survival. Pet ownStvdy: The current study was an independent project ership was an independent predictor of l-year survival complementary to the Cardiac Arrhythmia Suppression in a prospective study of 92 patients admitted to a coro- Trial (CAST) and CAST II. These studies constituted a nary care unit.’ The beneficial effects of pet ownership pharmacologic test of the arrhythmia suppression and for survival were independent of marital status or living mortality hypothesis. Twelve of the 27 CAST clinical situation. The generalizability of the relation of pet own- sites in the U.S. and I in Canada agreed to participate. ership to survival of patients with coronary artery dis- The CAST began in 1987 with the randomization of subease was limited by the small sample size, the nature of jects to 3 drugs, encainide, flecainide, or moricizinc, or the sample, and measurement techniques. Recent re- their matching placebos. When excess mortality was search has documented that the presence of a pet is asso- attributed to encainide and flecainide (April 19, 1989). ciated with decreased cardiovascular reactivity*.” to randomization was halted.“,’ The protocol was modified stressors, that this stress-reducing effect is greater than and permitted only the study of moricizine and its matchthe effect of the presence of a good friend,” and that ing placebo, CAST II.” The CAST II trial ended in Sepacquiring a pet leads to improved health status.4 Fur- tember 1991, and concluded that patients with ventricuthermore, in a large epidemiologic study, cardiovascular lar premature complexes after a myocardial infarction risk factors were greater among those who did not own should not be routinely treated with antiarrhythmic than those who owned pets.5 The current study further agents.8 investigates the effect of pet ownership on l-year surSubject recruitment: All patients who entered CAST vival among a well-defined group of post-myocardial or CAST II at each of the participating clinical sites durinfarction patients independent of the effects of physio- ing the period September 1987 to April 1993 were potenlogic, demographic. and other psychosocial variables. tially eligible for recruitment into the study. When the baseline information was transmitted to the CAST coorFrom the Department of Health and Nutrition Sciences, Brooklyn Coldinating center, the center randomly assigned subjects to Ieae ol CUNY Brooklvn. New York, and New Life Directions, Ellibe approached to participate in the stupy Additional i;-Cit Mavland. This study was supported in part by grants from informed consent was required for partlapation; 12% The De rto Society, Renton. Washington, Grant 5ROl NR02043-01 declined to participate. from the National Institutes ot rlealth, Bethesda; Maryland, and grants from the Professional Staff CongressCity University of New York, Procedure: Subjects were asked to participate in this New York, New York Research Award Program Manuscript received study while they were at the CAST clinical site. CAST May 9, 1995; revlsed manuscript received and accepted August clinical trial personnel recruited the participants and 30: 1995 administered all forms. At baseline, each subject comAddress for reprints: L&a Friedmann. PhD, Department of Health pleted the following indexes: social support questionand Nutrition Sciences, Brooklyn College of CUNY, 2900 Bedford Avenue, Brooklyn, New York 1 12 1 O-2889. naire-6 (SSQ6),” social readjustment rating scale.” pet
S
CORONARY
ARTERY
DlSf ASE/PET
OWNERSHIP
AND
SURVIVAL
IN CAST
1213
TABLE I Characterization Baseline Demographic
and
of 369 Participants According Physiological Variables
to
TABLE II OneYear Survival Cat Ownership (n = 369)
Variable
One-Year
Men White Black Married CAST active treatment Congestive heart failure Diobetes mellitus Education less than high school High school graduote Kollege graduate Retired Employed full time Age (yrl Survival Ejection Previous Runs of Values CAST
314 280 57 266 43 52 67 89 108 62 205 84 62.83
length (yr) fraction (%) myocardial infarction ventricular tachycordia ore expressed = Cardiac
(85.1) (75.9) (15.4) (72.1)
Ownership Status
(11.7)
(14.2) (18.9) (24.2) (29.3) (16.8) (55.6) (22.8) zt 9.17
‘p
1.62 i 0.59 38.19 * 9.63 144 (39.0)
86 (23.3)
es number
Arrhythmia
THE AMERICAN
w) or as mecm * SD. Suppression Trial.
JOURNAL
OF CARDIOLOGY3
VOL.
Survived (number subiects)
246
No pets Pets No dogs Doas No”cats Cats
ownership/attachment survey, state-trait anxiety inventory,” self-rating depression scale,‘* Jenkins Activity Survey,‘” and expression of anger scale.14 In addition, physiologic data including left ventricular ejection fraction, presence of myocardial ischemia, congestive heart failure, New York Heart Associdtion and Canadian Cardiovascular classifications, number of prior myocardial infarctions, presence of diabetes mellitus, and family medical history were obtained from the CAST coordinating center data bank. Mortality data were obtained by CAST clinical site personnel from physicians, family members, and medical records. One-year survivors were participants who were alive 1 year after baseline; nonsurvivors were those whose date of death was within 1 year after baseline. Inshvments: The SSQ6 was used to quantify both the amount of and satisfaction with social support perceived by a patient. The SSQ6 provides a list of 6 circumstances potentially requiring social support and asks the respondent who they could rely on for help in each situation (amount) and how satisfied they would be with the help they received in each situation (satisfaction).Y*1s*‘6 Persons who owned 1 or more dogs were classified as dog owners, and those who owned 1 or more cats were classified as cat owners. Pet ownership status was assessed with 1 item contained in a lo-item pet demographic questionnaire. The participant was asked to list the number and type of pets in the home and information regarding pet restrictions in the residence. The question, “Do any of the above pets belong to you?’ was used to classify persons as pet owners. Several psychosocial factors were also assessed at baseline: state and trait anxiety depression, anger expressed inward and outward, coronary prone behavior. and stressful life events occurring in the recent past and expected to occur in the near future. Subjects: A total of 424 subjects were recruited into the study. One-year survival status was obtained from 1214
Status
76
103
263 86 308 41
According
Survival
of
to Pet, Dog,
and
Status Died {number subiects)
16 4 19 1
17 3
of Chi-Square
1.07
4.05* 0.19
eo.05.
369 participants (87%). Of the 55 participants lost to follow-up, 54 (98%) had been followed for ~1 year when CAST II ended prematurely. A characterization of the subjects according to demographic and physiologic characteristics is included in Table I. One hundred twelve participants (30.4%) owned pets. This is somewhat lower than reports stating that 41 o/cof retired couples own pets and that the proportion of couples owning pets increases as the ages of the couples decreases.17The pet owners consisted of 87 persons who kept at least 1 dog and 44 who kept at least 1 cat; 24 of these pet owners kept both cats and dogs. Other pets included birds, fish, ducks, horses, snakes, and rabbits. Potential differences in baseline psychosocial and physiologic status between those who completed followup and those who did not were examined. The physiologic profile included ejection fraction, diabetes mellitus, runs of ventricular arrhythmias, medication group (active or nonactive), sex, and age. All psychosocial variables assessed at baseline were included in the psychosocial profile of participants. Neither physiologic (Wilks A = 0.9808, F [6,416] = 1.357, p = 0.231) nor psychosocial (Wilks X = 0.9652, F [lo,3961 = 1.43, p = 0.165) profiles of the 2 groups differed significantly. Statisiica~ analysis: Chi-square analyses were used to examine the univariate relation between pet ownership and survival status. The possibility that pet ownership made a significant independent contribution to survival, while controlling for physiologic severity of the illness, was examined. Logistic regression with physiologic severity and demographic variables (age, diabetes mellitus, left ventricular ejection fraction, runs of ventricular premature depolarization, and sex), the psychosocial variables, and pet ownership were entered simultaneously to evaluate the independent contributions of each variable. Similar logistic regression analyses were performed to assessthe effect of dog and cat ownership both individually and in combination on survival status. A stepwise hierarchical logistic regression was used to examine the effects of physiologic variables (step 1). social support amount (step 2), and cat ownership (step 3) on survival. Differences in physiologic status between those who own and do not own dogs and those who do and do not survive were examined with a 2-way multivariate analysis of variance. Multivariate analyses of variance were used to examine differences in physiologic and psychosocial status between dog and cat owners. DECEMBER
15. 1995
RESULTS
Twenty of the 369 participants (5.4%) in the study died within 1 year. When the frequency of deaths among pet owners and non-owners was compared, there was no significant relation between pet ownership and l-year survival (see Table II). The frequency of dog and cat ownership was sufficient to examine each separately in relation to survival status. There was a significant univariate relation between dog ownership and survivd (chi-square [l degree of freedom (df), n = 3691 = 4.05, p = 0.044; Table IT) but not between cat ownership and survival. Dog owners were more likely to be alive I year after baseline assessment than people who did not own dogs. Pet ownership and survival: The combination of physiologic and psychosocial variables and pet ownership was 95.74% accurate at predicting membership in the correct survival group; 99% accurate for survivors and 37% accurate for nonsurvivors (chi-square 11 df, n = 711 = 77.44, p <O.OOOl). As expected, physiologic variables (ejection fraction, diabetes mellitus, and runs of ventricular premature beats) were significant, independent predictors of survival. Pet ownership tended to be independently related to survival (p = 0.085). In the logistic regression analysis, when the effects of physiologic and other psychosocial variables were controlled, pet owners tended to be more likely to survive 1 year than nonowners. The specific psychosocial variables that contributed to prediction of survival were then examined. The amount of social support also made a significant independent contribution to survival. Participants with greater amounts of social support were more likely to survive 1 year, controlling for the effects of all other psychosocial and physiologic variables. Two additional psychosocial variables tended to make independent contributions lo survival status: lower state anxiety (p = 0.087) and greater expectations of future life changes (p = 0.065). Dog owners, cat owners, and survival: Physiologic and psychosocial variables and cat and dog ownership were entered into a logistic regression equation to prcdiet l-year survival status. Survival status was predicted well: 17.5% of the variance in survival was explained as: (model chi-square [df 18, n = 352]= 75.93, p <O.OOOl; goodness of tit [df 3333 = 103.42, p = 1.00). The combination of these variables predicted survival status correctly 95.7% of the time. Survival status was predicted correctly for 98.8% of those who actually survived I year and for 42. I o/cof those who actually died within 1 year. As would be expected, physiologic variables were the best independent predictors of survival: ejection fraction (R = -0.2352, p = 0.0007, Exp[B] = 0.X688), runs (R = -0.2211, p = 0.0012. Exp[B] = 0.1167), and diabetes mellitus (R = -0.1652, p = 0.014, Exp[BJ = 0.1658). Dog ownership made a significant independent contribution to survival status (R = 0.1204, p = 0.02, Exp[B] = 0.0687). Social support also tended to be related to survival status (R = 0.0628, p = 0.05, Exp[B] = 0.9355). Increased likelihood of l-year survival was associated with higher ejection fractions, not having diabetes mellitus, not having runs of ventricular premature beats, not owning a cat, owning a dog, and having greater amounts (:OROILARY
of social support. Thus dog ownership made a significant positive contribution to survival status, while controlling for cat ownership, physiologic status, and the other psychosocial factors, including social support. Dog owners and surv’nral:Physiologic and psychosocial variables and dog ownership were entered into a logistic regression equation to predict l-year survival status. Survival status was predicted well: 24% of the variance in survival was explained (model chi-square [df 17, n = 352]= 70.84, p <O.OOOl; goodness of fit [df 3341 = 156.28. p = 1.0). The combination of these variables predicted survival status correctly 96% of the time. Survival status was predicted correctly for 99. I ‘-ZJof those who actually survived 1 year and for 42.1% of those who actually died within 1 year. As would be expected, physiologic variables were the best independent predictors of survival: ejection fraction (R = -0.2538: p = 0.0004, Exp[B] = 0.8697), runs (R = -X).2253, p = 0.001, ExplB] = 0.1243), and diabetes mellitus (R = -0.1496, p = 0.01, Exp[B] = 0.1957). Among the psychosocial variables, dog ownership (R = 0.0720, p = 0.05, Exp[B] = 0.1068) and the amount of social support (R = 0.0508. p = 0.05, Exp[B:I = 0.9420) made significant independent contributions to survival status. Increased likelihood of 1-year survival was associated with higher ejection fractions, not having diabetes mellitus, not having runs of ventricular premature beats, owning a dog, and having greater amounts of social support. Thus, dog ownership made a contribution to survival slatus, while controlling for both physiologic status and the other psychosocial factors, including social support. Health status, dog owners, and survival: Researchers have previously suggested that any differences in health status between pet owners and non-owners could be a result of healthier people choosing to own pets, particularly dogs. The current study afforded one the opportunity to examine this explanation directly among a group of patients with coronary artery disease. Physiologic profiles of people who do and do not own dogs and those who do and do not survive were compared. There is no evidence that differences in physiologic status of dog owners and non-owners are responsible for the differences in 1-year survival between those who do and do not own dogs (Wilks A = 0.977, F [6,359] = 1.41. p = 0.21). The physiologic profile of those who owned dogs did not differ significantly from that of those who did not (Wilks X = 0.985, F [6,359] = 0.94, p = 0.47; see Figure 1). As would be expected, the physiologic profile of those who survived was significantly different from that of those who did not (Wilks A = 0.925, F [6,X9] = 4.84, p <O.OOl. see Figure 2). Cat owners and survival: Physiologic and psychosocial variables and cat ownership were entered into a logistic regression equation to predict l-year survival status. Survival status was predicted well: 25.6% of the variance in survival was explained (model chi-square Idf 17, n = 3521 = 69.77. p <O.OOOl; goodness of fit [df 334) = 136.29, p = 1.00). The combination of’ these variables predicted survival status correctly 96% of the time. Survival status was predicted correctly for 99.1 %Jof those who actually survived I year and for 42.1% of those who actually died within 1 year. Increased likelihood of sur-
ARTERY DISEASE/PET
OWNERSHIP
&Nil
SCIR’~~lVr\L IN CAST
1215
viva1 was associated with higher ejection fraction, not having diabetes mellitus, not having runs of ventricular premature beats, being a man (R = 0.1516, p = 0.02, Exp[B] = 5.76) and not owning a cat (R = 0.1601, p = 0.03, Exp[B] = 8.01). Cat ownership contributed to survival contrary to the hypothesized direction. Cat owners, social support, and survival: The interrelation of social support, cat ownership, and survival was examined more closely. When the independent effect of social support was entered before cat ownership, cat ownership did not m‘ake a signilicant contribution to survival. Thus, the relation of cat ownership to survival was not independent of social support. Dog owners, cat owners, and physiologic status: Physiologic profiles of participants who owned only cats and participants who owned dogs were compared. Physiologic profiles of the 87 persons who owned dogs did differ from the profiles of the 20 who owned only cats (F [6,115] = 2.605, p = 0.012). The difference was largely in the sex of the subjects: 11.4% of the cat owners were women compared with 6.9% of the dog owners. The psychosocial profiles of the dog and cat owners did not differ (F [10,10X] = 0.9245, p = 0.514). DISCUSSION
In this study of 369 participants in CAST who were followed for at least 1 year, dog ownership and social support made significant independent contributions to survival beyond the effects of the physiologic measures of the severity of the cardiovascular disease. These pos100.0 90.0
,
1 m 0
DOG OWNERS DOG NON-OWNERS
itive findings support and increase the generalizability of the previous finding that pet ownership was related to survival of patients with coronary artery disease, independent of social supporti Dog ownership and amount of social support were independent predictors of survival. Although owning a dog had a positive influence on health, that effect was complimentary to, rather than a substitute for, other sources of social support. In contrast, cat ownership was not related to survival and was not independent of social support. Based on the current study, one should not conclude that cat ownership is harmful. It is likely that differences in other characteristics are responsible both for cat ownership and the apparent lower survival of cat owners. In a recent study,” cat owners were significantly more likely to be sedentary than people who owned dogs and those who did not own any pets. Although the current study did not include assessment of exercise habits, it is possible that sedentary persons were less likely to survive. Investigation of the relation of cat ownership to other factors that might also be related to survival was possible. None of the women who owned cats also owned dogs, whereas 24 of the 39 men who owned cats also owned dogs. Examination of differences between cat and dog owners revealed that while the psychosocial proliles of the 2 groups did not differ, the physiologic profiles did. A much higher percentage of cat (11.4%) than of dog (6.9%) owners were women. Overall, women had higher 1-year mortality (p ~0.01, hazard ratio = I .9) than men in CASTi Because only 5 women owned cats, further study is necessary to quantify the interrelation between survival, social support, and cat ownership. Attachment to a pet may be responsible for differences in cardiovascular benetits of pets among pet own-
80.0 100.00 90.00
I 0
SURVIVORS NON-SURVIVORS
* p < .05
80.00 ~
70.00
50
60.00
B a.
50.00
8 3
*
r
40.00 30.00 20.00 1.50 0.75 0.00
PHYSIOLOGICAL
PROFILE
FIGURE 1. Comparison of baseline p siologic profiles of participants who owned (n = 87) and di t not own (n = 272) dogs. Age is expressed in years; EF = rcent left ventricular ejection fraction; HIST MI = history of at reast 1 myocardial infarction before the Cardiac Arrhythmia Suppression Trial qualifying myocardial infarction; NYHA = New York Heart Association congestive heart failure classification. RUNS = having runs of ventricular tachycardia on 2bhour Holkr monitor.
1216
THE AMERICAN
JOURNAl
OF CARDIOLOGY’*
VOL.
PHYSIOLOGICAL
PROFILE
FIGURE 2. Comparison of baseline physiologii profiles according to survival status; the 349 tlicipants who were alive 1 year after baseline (SURWORSYcom~red with the 20 participants wha died within 1 year of ba ine (NGN-SURWGRS). Age is expressed in years. Abbreviations as in Figure 1.
76
DECEMBER
15,
1995
1
ets.lg In the current study, pet ownership was defined as claiming a pet as one’s own rather than just having a pet in the household. Whereas those who own both dogs and cats have been reported to have less attachment to their cats than their dog, this difference does not appear to be responsible for the observed differences in mortality between dog and cat owners. In the current study, among men who owned only cats, the mortality rate was significantly higher (2 of 15) than among those who owned dogs with or without cats (0 of 81). There were no large differences in mortality among women (1 of 5, 1 of 6, respectively). In the current study, social support was the only psychosocial variable, in addition to dog ownership, that was an independent predictor of survival. Patients with greater amounts of social support, as measured on the &item SSQ6 scale, were more likely to survive than those with lesser amounts. This finding is consistent with the multivariate findings for the 647 participants in the CAST placebo groupI in which social support, as measured with 1 item, was the only baseline psychosocial variable that was related to survival in multivariate analysis. It was also consistent with the findings for the 194 men and women in the Established Populations for the Epidemiologic Study of the Elderly Population who were hospitalized with myocardial infarctions in 2 New Haven hospitals.Z0 In that study the number of persons available to provide support, but not integration into social networks, was related to survival. In these studies, the type of social support that was related to survival was a measure of the availability of other persons to provide support when needed. This contrasts with other types of social support that include satisfaction with social support (the current study*‘), the amount of support patients thought they actually needed, and integration into social networks,*O which were not related to survival of patients with coronary artery disease. The powerful detrimental drug effects in CAST made it a difficult vehicle for evaluating the impact of psychosocial factors on survival.lx This problem was minimized in the current study because most patients (88.3%) were not taking active medication. Furthermore, there were no significant difierences in the distribution of active medication between pet owners (12.5%) and nonowners (10.9%). Pets are theorized to act as buffers to stress. Pet ownership is proposed to afford several benefits to their owners including decreases in anxiety** and sympathetic nervous system arousal2,‘9 in response to stressors. In addition, people who acquire pets report improved health over the subsequent months compared with controls,4 and pet owners receiving Medicaid make fewer visits to their physicians than non-owners.23 These studies concur with the current study in supporting better health status or outcome among pet owners than among non-owners. It has been suggested that dog owners may be healthier than owners of other pets, and thus the better survival among dog owners is a reflection of their better physiologic status. The basis for conjecture is that caring for a dog often requires more work than that needed to keep other pets. Accordingly one would expect differences in physiologic status between dog owners and CORONARY
those who did not own dogs to account for the increased likelihood of survival ‘among dog owners. This conjecture was not supported in the current study. There were no differences in physiologic status between those who own dogs and either all subjects or owners of other pets. Furthermore the contributions of pet and dog ownership to survival were independent of the contributions of the physiologic factors that predict survival. The current study provides strong evidence that pet ownership, and dog ownership in particular, promotes cardiovascular health independent of social support and the physiologic severity of the illness. Additional research with larger samples is needed to investigate interrelations between cat ownership, social support. and cardiovascular health.
1. Frizdmann year survival
E, Katcher of patients
Rep I YL(O;95:307-3
AH, Lynch JJ, Thomas SA. Animal companions and one after discharge from a coronary care unit. pubuhlic /feat01
12.
2. Friedmann E, Katcher tion and blood pressure: 1983;171:461-465. 3. Allen KM, Blascovich pet dogs as moderators of
chol
AH, Thomas the influence J, Tomaka autonomic
SA. Lynch of animal
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JJ. Messent companions.
PR. Social
interac-
J Nen~ Menr
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RM. Presence of human friends and to stress in women. J Pm Sot Ps!
1991:61:582-589.
4. Serpell
JA. Beneficial
effects
of pet ownership
on some aspects of human
health
JR So< .&fed 1991:X4:717-720. 5. The Cardiac Arrhythmu Slippression I’rial (CAST) Investigators. Preliminary report: effect of encainide and tlecaimde on mortality in a randomfxd trial of arrhythmia suppression after mytrardial infarction. IV Erlgl J Med 1989;321:
4(H% 12. 6. Anderson
W, Reid P, Jennings tiL. Per ownership and risk factors for cardiovascular disease. Med J Ausr lYY2:157:298-301. 7. Echt DS, Liebson PR. Mitchell LB, Peters RW, Dbias-Manno D, Barker AH. Arensbere D. Baker A. Friedman L. Greene HL. Hunter ML. Richardson DW. Mortality and morbidity in patients receiving encainide. tlecainide. or placebo: the Cardiac Arrhythmia Suppression Trial. N Engl J Med 1YY1;324:781-788. 8. Greene HL, Rod&DM. Katr RJ. Woo&y RL. Salerno DM. Henthom RW. The Cardiac Arrhythmia Suppression Trial: First CAST...then CAST-II. JAm Co/l Cur-
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9. Sawa; IG. Samson BR. Sheann EN, Pierce G. A brief mcaswe of social nlpponpractical and theoretical implications. J Sot Pm Relarim~hip.~ lYX7:4:497- -5 10. 10. Holmes TH, Rahe RH. The social readjustment rating scale. J Psyhosorn RF> 1967;11:21~218. 11. Spielberger CDP, Lushene RE. Gonuch RL. STAl Manual. Palo Alto, CA Consulting Psychologist Press. 1072. 12. Zung WK. A self wing depression scale. Arch (;un Psvchiufryv lY65;12:63-70. 13. Jenkins CD, ZyLanski SJ, Rosenman RH. Jenkins Actiiity Survey Manual. Neu York: Psychological Corporation, lY79. 14. Spielkrger CD, Johnson EH. Russell SF, Crane RJ. Jacobs JA, Worden TJ. The experience and expression of anger: construction and validaiion of anger expression scale. In: Chewy MA, Rosenman RH, eds. Anger and Hostility in Cardiovascular and Behavioml Disorders. New York: Hentisphere/McGmw Hill, lY85:5-30. 15. Samson IG. Levine MM. Basham RB. Samson RR. Assessing social support The Social Suppwt Quesrionnaire. J Pars Sor P.&w/ lY83;44: 127-139. 16. Samson IG, Sarason BR. Shcann EN. Social suppln as an individual difference variable: its stability, origins. and relational aspects. J Pm Sot kyhol IY86;50:845-855. 17. Rowan A. Companion animal demographics and unwanted animals in the l!nit. ed States. Anrhrozoo.s lYY2;5:222--225. 18. Gorkin L. Schron EB. Brooks MM, Wiklund I. Kellen J. Vcner J, Schoenbcrgcr JA, Pawitan Y, ,Monis M, Shumaker S. Psychosrxial predictors of monality in the Cardiac Arrhythmia Suppression Trial- I (CAST-l). Am JCurdiol lY94;7 I’
263-261. 19. Friedmann E. The role of pets in enhancing human wellbeing: physiological effects. In: Robinson 1. ed. Waltham Book of Human Animal Interactions. Oxford Pergamon. 1995333-53. 20. Brrkman LF, LetrSummeru L, Horwiw RI. Emotional suppon and survival after myocwdial infarction. Ann Inwnr Mcd lYY2;l 17:1003-1009. 21. Williams RB, Barefoot JC. Califf RM, Haney TL, Saunders WB. Pryor DB. Hlatky MA. Siegler IC, Mark DB. Prognostic importance of social and economic resources among medically treated patients with angio~raphically documented COTUnary artery direaae. JAMA lY92:267:52W525. 22. Wilson CC. ‘The pet as an nnxiolyllc intervention. J Nen: MLW Di.v 1991; I79
482-489. 23. Siegel JM. Stressful ly: the moderating
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life events and use of physician services among the elderrole of pet ownership. J PKS Sot P.swho/ 1990;%:1081-10X6.
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AND
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