Prevalence of Rheumatoid Arthritis in Alaskan Eskimos

R. Palmer Beasley. MD, Henry Retailliau, and L. A. Healey. MD

A rheumatoid arthritis prevalence survey was conducted in eight Alaskan Eskimo villages during the summer of 1970. Eleven cases of definite rheu- matoid arthritis were found among 1443 Eskimos over 14 years of age. The frequency of 1.0% among adult females and 0.5% among adult males is almost identical with the National Health Examination Survey prevalence estimate for the general United States.

Epidemiologic comparisons of populations with differing rates of a disease have frequently led to important understanding of its natural history and sometimes the etiology. Although the prevalence of rheumatoid arthritis (RA) has been studied in numerous and diverse pop- ulations around the world, the epidemiologic approach has been thwarted by the striking uniformity of the prevalence of the disease from population to population and place to place ( I - 19). A recent study, however, has shown that Yakima Indians in Washington State have an unusually high prevalence of RA and that the increased prevalence is principally due to cases in young women (20). In the spring of 1970 we learned that physi-

cians at the Alaska Native Health Service Hos- pital in Anchorage believed that they were seeing an unusual number of cases of RA. These physicians did not believe the problem was confined to any particular group or area in Alhka. A survey of RA prevalence among Es- kimos by Blumberg et af in 1961 did not sug-

Fmm the Dcpartmcnt of Epidemiology and International Heal&, School of Public Health and Community Medicine, University of Washington. and the Virginia .Mason Re- rearrh Center, Seattle, Washingon.

Sllpponcd by a grant from 51rs. Edith Bullock of An- chorage, Alaska, to he Virqinia Mason Research Center.

Rcprint requests should be a d d d to Division of Anhritb, Univmitvof Washington. Seattle, W.498105.

Submitted for publication hug I, 1972; amptcd July 2,1973.

gest an unusual prevalence of rheumatoid arthritis (2). These authors examined 219 res- idents of the village of Wainwright. of whom 92 were over age 19. While 10 of 74 adult sera in Wainwright gave positive tests for rheuma- toid factor by the bentonite flocculation method (BFT), only one definite case of RA was found. In the present study performed in 1970, we ex- amined a larger number of Eskimos and con- firmed the findings of Blumberg and co- workers.

MATERIALS AND METHODS Background and Population

Alaska is divided by the Native Health Service into seven service units. The Kotzebue service unit located in the northwestern part of the state larp;ely above the Arctic circle was arbitrarily selected for this study. This traditional Es- kimo region has an area of approximately 78,900 square mila and a total population of 10,183. (All population fiq- urcs are derived from the 1970 census). Of these. 8 2 5 were Eskimo, 17% wereCaucasian, 0.3% were Neqro. and 0.3% were Indian. Virtually all persons in this desolate part of Alaska live in well-defined and .fairly compact villages. One-family wood frame houses have qenerally replaced the traditional sod huts. Twenty-wen such villaqes are spread throughout the area. some on the coast, others on inland riven, and t h m on islands. Boat, doq sled. snowmobile. and plane provide transportation between villaqes: Mail service by air reaches most villaqe several times a week. in some p lam daily. Paucnqers and carqo often qo by mail plane to and from villaqes.

Eight villaqcs were selected for studv: Cambell. liiana, Kwalina, Noatak, Noowik. Savoonga. .%lewick. and L'na-

Mhritk and Rheumatism. Vol. 16. No. 6 (November-Ikcemkr 1973) 737

BEASLEY Ef AL

I ak la . These represented the largcn villages in the area except for Nome, Kotzebue and Point Hope. Nnme and Kotzcbuc were exduded because they are not typical, and Point Hope because it had mcntly been surveyed for an- other problem. The combined Eskimo population of thex eight villatp was 2,725, amounting for 33% of the popu- lation in the Kotzebuc s m k area.

Most Ndical care in the villages is rendered by health aides trained in Kotzebuc and Anchnrage Public Health Service hospitals. Most villaqes have two aides. Each village. has an up-to-date clinic facility. with a radio. Radio “rounds” are conducted daily by one of the physicians at the Kotzebue Hospital. Patients with problems rquirinq physician contact are evacuated by air to Kotzebue or Nome.

Diagnostic Criteria All persons identified as having RA in this rrpon met

CIOMS (Rome) modification of the ARA criteria. for dcfi- nite d w .

Survey Techniques A mord review for pcmns given a diagnosis of R.4

within the past 6 ycan was conducted in the Anchorage and Kotzebuc Hospitals. The aides in each village were con- tacted by radio in advance and asked to prepare a list of vil- lage residents (whcrher or not present at the mnment) who had difficulties with the* joints. On arrival in the village the examiner was taken to SCC all persons with ,joint prob- lems and those on the lists derived from the hospital searches. When thew exams were completed a house-to- h o w SUN^ was conducted. An attempt was made to incer- view all persons over 14 years of age living in the villaqc. Family data, ,joint complaints. and physical findin.@ were recorded on a standard form. A blood sample was requested from each individual. S-rays wem not obtained. The aides served as interpreters for persons not speaking English. In each caw they knew all membrrs of the village. and the resi- dents were already acquainted with the general purpnse of the visit at the time of our arrival. Reluctance to participate was ram. usually encountered in young men. .%me villaqe members were not seen. usually duc to absence fishinq or berry-gathering, but all persons reported by the aides to have significant arthritis were examined.

*The CIOMS criteria was desiqned for epidemiolnqir studies and essentially eliminates those aspects of the A R A clinical criteria which are not feasible in field studin. such as joint biopsies. T o qualifv as definite RA a patient must Score at least 5 of 8 possible points. Each cf the followinq is worth one point: Morninq stiffness, pain or tenderness. soft tissue swellinq one joint. soft tissue swellinq of an additional joint. symmetrical swellinq. nodule, x-ray changes, and positive rheumatoid factor test.

Examination of persons without joint symptoms was l i m ited to hands and wrists. Other joints were examined as in- dicated by patient’s complaints. Hips were not examined.

Interviews were conducted by IWO of us (RPB and HR). one a medical student sprcially instructed in mqn iz ing rheumatoid arthritis. Patients in whom the diagnosis was in doubt were also sccn by RPB. All but one casc classified as RA were Ken by both and the diaqnosis concurred.

Serology All x r a were screened without heating using a slide latex

test and those showing 3+ or 4+ reaction tested funher by bentonite flocculation (BFT), in which the sera are heated prior 10 testing x r a with a BFT. Reaction in a dilution of 1 3 2 or greater was considend positive.

RESULTS A total of 897 of the 1443 adult residents

(62.7%) of eight northern Alaskan Eskimo vil- lages were examined for RA. Eleven persons were found who fulfilled the ARA criteria for definite RA, representing an overall prevalence between 0.8% and 1.2% depending on whether the total or thePxamined population is taken as the denominator. \Ye believe the total popu- lation determined from the 1970 census is most appropriate since we were able to examine all persons known to have serious arthritis. Fur- thermore, no cases of serious arthritis in addi- tion to those known to the health aides, were discovered in the house-to-house survey. Usins the census denominator, the prevalence of RA among persons over age 14 was 1.0% for fe- males and 0.3% for males. The rates by a g for each sex are shown in Table 1.

The overall prevalence of rheumatoid factor (BFT) by age and sex is shown in Table 2. The frequency increased with increasinq hge. but unlike RA, it was equally frequent in males and females. Of the 31 persons with a positive test, 7 had definite R.4, 20 had joint complaints from other causes, and 24 had no joint problems (Table 3). Thus only 14% of positive rheuma- toid factor could be attributed to Rh.

Twenty-one percent of the adult Eskimos had ever had joint problems: 0.8% due to R.4 and 19.9% to other causes. The proportion who

738 Arthritis and Rheumatism. V d . 16, No. 6 (November4hcernbor W73)

RA IF) ALASKAN ESKIMOS

la#. l. Prevalence of Rheumatoid Arthritis by Age and Sex

Population

Seen Rheumatoid arthritis 1970

Age census No. % No. Sb

MaleS 15-24 25-34 35-44 45-54 5 5 6 4 65 + Unknown TOTAL

252 145 153 92 62 70 0

774

124 49.2 1 0.4 70 48.3 1 0.7 97 63.4 0 0 56 60.9 0 0 41 66.1 0 0 55 78.6 2 2.9

447 57.8 4 0.5 4

Females 15-24 224 113 50.4 0 0 25-34 122 88 72.1 0 0 35-44 118 73 61.9 0 0 45-54 69 58 84.1 1 1.4 55-64 69 61 88.4 3 4.3 65 + 67 48 71.6 3 4.5 Unknown 0 5 TOTAL 669 446 66.7 7 1 .o

had had joint problems was 25% for females and 17.4% for males. The frequency of joint complaints incr&ed with increasing age for both sexes. The proportion of persons with R.4

was approximately constant amon8 those with joint complaints in each aqe group.

Table 3 shows the distribution of rheumatoid factor according to age and clinical status.

Table 2. Prevalence of Rheumatoid Factor by Age and Sex

Females Males Total

RFPosITotal % RFPos/Total % RFPosITotal %

15-24 25-34 35-44 45-54 55-64 65 + Unknown

31113 2.7 11124 0.8 4/237 1.7 4/88 4.5 1/70 -1.4 5/158 3.2 2/73 2.7 7/97 7.2 91170 5.3 1/58 1.7 3/56 5.4 41114 3.5 6/59 10.2 5/41 12.2 11/100 11.0 8/48 16.7 9/55 16.4 171103 16.5 011 3 111 1 1/24

TOTAL 24/452 5.3 271454 5.9 51/906 5.6

Arthritis and Rheumatism. Vol. 16. No. 6 (November-December 1973) 739

Table 3. Prevalence of Rheumatoid Factor by Age and Clinical Status

Clinical status

Joint symptoms

Age RA No RA

15-24 o/ 1 0112 25-34 111 0117 3544 010 3/39 45-54 111 1/28 55-64 313 3/44 65 + 215 13/36 Unknown 010 011

No joint RF attributable symptoms Total to RA

41224 41237 014 41140 511 58 115 6/131 91170 0/9 2/85 411 14 114 5/53 11/100 311 1 2/62 171103 2/17 1/23 1/24 011

TOTAL 711 1 2011 77 24/718 51/906 7/51

Crude rate 63.6% 11.3% 3.38 5.6% 13.7%

Age adjusted rate 7.0% 3.7% 5.7%

*Numbers too small for rate adjusted.

Sixty-four percent of persons with rheumatoid arthritis had a positive rheumatoid factor. The age-adjusted frequency of rheumatoid factor was 7.0% among nonrheumatoid patients with joint complaints and 3.7% among patients with- out joint complaints, P > -03.

having arthritis by the health aides. Of the re- maining village residents examined. no addi- tional cases of RA were discovered. \Ve there- fore estimate the prevalence of definite Re\ among Eskimos of the Kotzebue area to be 0.8%. This rate is almost identical with esti- mates for the United States derived from the

DISCUSSION This study was undertaken because prelimi-

nary information suqgested that Alaskan na- tives might have an unusually high prevalence of RA. The only previous study had not shown an unusually high prevalence. but the popula- tion examined had included only 92 adults (3). In this study was examined 63% of the 2725 adult Eskimo residents of eight villages in northwest Alaska. Eleven persons were found who fulfilled the ARA epidemiologic criteria for definite RA. We believe it unlikely that we missed cases among those not examined (37%). We examined all persons who were identified by village health aides as sufferinq from serious joint problems. All cases we diagnosed as hav- ing definite RA were among those identified as

National Health Examination Survey (NHES). As with the NHES. the rate among Eskimo females was twice that for males.

Diagnoses in this study were based on clini- cal examinations plus serology. without the benefit of x-rays. Although x-ray results would have been of interest. they would not have al- tered the prevalence estimates for definite Rh presented here. because even with positive x- rays, there were no other persons with enough clinical points to have been classified as definite RA.

Of the Eskimos tested. 5.6% had rheumatoid factor. .As in the National Health Examination Survey. persons with joint complaints without having definite Rh were more frequently rheu- matoid factor positive than persons without joint complaints, but in neither population was

740 Arthritis and Rheumatism. Vol. 16, No. 6 (November-December 1973)

RA IN ALASKAN ESKIMOS

this difference statistically significant. As has been frequently observed in other populations the frequency of positive rheumatoid factor was equal in males and females. even though fe- males were afflicted with definite RA twice as often as males. Rheumatoid arthritis accounts for only a small proportion of persons with pos- itive rheumatoid factor tests, in this study only 14% could be attributed to definite RA and 49% of those with positive tests had never had joint problems. The figures for the National Health Examination Survey are remarkably similar: 9% of those with rheumatoid factor havinq defi- nite RA and 56% beins without joint problems.

Fewer Eskimos had any joint complaints than persons in the NHES. Seveiity-nine per- cent of Eskimos said they had never had symp- toms, compared to 64% of persons in the NHES. As with persons elsewhere in the United States, Eskimos with joint problems tended to relate exacerbations of their symp- toms to cold weather and chanqe in climate. even though Eskimos mean by this much greater extremes than most people in the United States.

The prevalence of RA has also been esti- mated in other North American native popu- lations. As in the present study, the prevalence was not unusual in the Eskimos of Wain- wright (2), the Haida of Queen Charlotte Island, British Columbia (4), the Blackfeet in Montana, or the Pima in Arizona (10). By con- trast, young women of the Yakima Indian tribe in Washington state do have a significantly higher prevalence (3.4%) (20).

ACKNOWLEDGMENTS The authors would like to acknowledqe Dr. J . K. Flesh-

man of the Alaska Native Health Service fnr suqqcstinq thew studies, and Dr. Keith Hooker. previouslv Service Unit Director at the Alaska Native Health Service in Kot- zlbue. for facilitating them.

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