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Biomedical subjects

J F Kurtzke

Publications and source records attributed to J F Kurtzke.

At least 19 recordsLinked to original sources
PubMed2005

Further considerations on the distribution of multiple sclerosis in Sweden.

OBJECTIVES: The geographic distribution of multiple sclerosis (MS) in Sweden over time was compared in order to analyze homogeneity. METHODS: The distribution of MS was compared among three nationwide resources: 1301 hospital cases 1925-1934; 5425 deaths 1952-1992; and 11,371 disability pension recipients 1971-1994. RESULTS: Distributions by county (lan) were markedly non-homogenous, with greatest variations in the early prevalence series (16-232% of the national mean), less within the death data (75-170%), and least for the disability series (87-128%). Maximal rates for MS in the early prevalence series were found for the cluster of seven counties surrounding the two major lakes of south central Sweden, as well as for one region on the northern shore of the Bay of Bothnia, and another also off the Bay north of Stockholm. CONCLUSION: Though the epidemiologic sources are quite different, they are internally consistent and thus provide three consecutive cross-sectional views of the distribution over time. When considered together the data may be compatible with a thesis of the origin and spread of MS within Sweden from the south-central inland lake regions of the country. Such spread within a half century is too rapid for a genetic cause, including HLA patterns.

Adolescent↗
PubMed2001

Multiple sclerosis in the Faroe Islands: an epitome.

The Faroe Islands are a semi-independent unit of the Kingdom of Denmark and are located in the North Atlantic Ocean between Norway and Iceland. Efforts to identify all cases of multiple sclerosis (MS) since 1900 among Faroese have been continuing for over a quarter century. As of 1998 prevalence was 66 per 100,000, age adjusted to 1960 US population, with a rate of 100 for women and 34 for men. Median survival was at 29 to 34 years with no significant difference by sex. Faroese with overseas residence indicated that at least 2 years of exposure from age 11 on in a high-risk area are required for acquisition of MS. Among native resident Faroese the first instance of symptom onset was in 1943, heralding a type 1 epidemic of 21 cases. This was followed by three successive epidemics of 10, 10, 13 cases, with membership in each epidemic defined by calendar time and age of exposure. Age at exposure for epidemic I was 11 to 45 years; for later epidemics age 11 was the minimum. We believe the source of MS on the Faroes was their occupation by British troops for 5 years in World War II. We think they introduced a widespread, specific, persistent (but unknown) infection, probably asymptomatic, which we call the primary multiple sclerosis affection (PMSA). Only a small proportion of those affected with PMSA will years later show any clinical signs of MS. Models of transmission of PMSA through successive cohorts of Faroese fit the data for epidemics II and III, and predicted the occurrence of epidemic IV. The Faroese provide an ideal location to determine the nature of PMSA, since the disease has remained geographically stable for 50 years without further spread throughout the islands.

Adult↗
PubMed2000

Epidemiology of multiple sclerosis in US veterans. VIII. Long-term survival after onset of multiple sclerosis.

Survival to 1996 was analysed for nearly 2500 veterans of World War II who were rated as 'service-connected' for multiple sclerosis as of 1956 by the then Veterans Administration. Survival from onset was defined for all white women and black men, and a random sample of white men. Median survival times from onset were 43 years (white females), 30 years (black males) and 34 years (white males). Crude 50-year survival rates were 31.5% (white females), 21.5% (black males) and 16.6% (white males), but only the white females and white males were significantly different. A proportional hazard analysis was used to identify risk factors for mortality from multiple sclerosis onset year. Significant risk factors included male sex (risk ratio: 1.57), older age at onset (risk ratio: 1.05 per year) and high socioeconomic status (risk ratio: 1.05 per socioeconomic status category). There were no statistically significant differences in survival following multiple sclerosis onset by race or latitude of place of entry into military service, both significant risk factors associated with the development of multiple sclerosis. Standardized mortality ratios utilizing national US data (for 1956-96) showed a marked excess for all three race-sex groups of multiple sclerosis cases, with little difference among them, but with a decreasing excess over time. Relative survival rates, used to compare the survival of multiple sclerosis cases with that of other military veterans, did not differ significantly by sex-race group, nor by latitude of place of entry into military service, but did differ significantly by socioeconomic class. The lack of difference in male and female relative survival rates suggests that the significant difference in survival between male and female multiple sclerosis cases is, at least in part, a result of sex per se and not the disease.

Adult↗
PubMed2000

Multiple sclerosis in time and space--geographic clues to cause.

Geographically MS describes three frequency zones. High frequency areas (prevalence 30+ per 100 000) now comprise most of Europe, Israel, Canada, northern US, southeastern Australia, New Zealand, and easternmost Russia. Medium frequency areas include southern US, most of Australia, South Africa, the southern Mediterranean basin, Russia into Siberia, the Ukraine and parts of Latin America. Prevalence rates under 5 per 100 000 are found in the rest of Asia, Africa and northern South America. Migrants from high to lower risk areas retain the MS risk of their birth place only if they are at least age 15 at migration. Those from low to high increase their risk even beyond that of the natives, with susceptibility extending from about age 11 to 45. Thus MS is ordinarily acquired in early adolescence with a lengthy latency before symptom onset. MS occurred in epidemic form in North Atlantic islands: probably in Iceland and the Shetland-Orkneys; clearly in the Faroe Islands. In the Faroes first symptom onset was in 1943, heralding the first of four successive epidemics at 13 year intervals. The disease was presumably introduced by occupying British troops during World War II, with the postwar occurrences representing later transmissions to and from consecutive cohorts of Faroese. What was transmitted is thought to be a specific, widespread, persistent infection called PMSA (the primary multiple sclerosis affection) which only rarely leads years later to clinical MS. Search for PMSA is best attempted on the Faroes where there are regions still free of MS after 50 years.

Disease Outbreaks↗
PubMed1998

Multiple sclerosis in North African migrants to France.

Among some 7500 respondents with known place of birth who had completed a nationwide questionnaire survey for multiple sclerosis (MS) in France in 1986, there were 260 born in former French North Africa (Algeria, Morocco, Tunisia). They had migrated to France between 1923 and 1986, but 66% came between 1956 and 1964. Two-thirds were from Algeria, where virtually the entire European population had emigrated in 1962 at the end of the Algerian war for independence. The migrants were younger at prevalence day (mean 43.4 years) and at onset (29.4 years) than the French-born MS (46.6; 31.3 years). Eight migrants lacked age information. The 225 migrants with onset more than 1 year after immigration presumably acquired their MS in France. They provided an age adjusted (US 1960) MS prevalence rate 1.54 times that for all France. If the latter is taken at 50 per 100,000 population their estimated adjusted rate is 76.8 with 95% confidence interval of 67.1 to 87.5. The other 27 with presumed acquisition in North Africa gave an estimated adjusted prevalence of 16.6 per 100,000 (95% CI 10.9-24.1). For those migrants with acquisition in France there was a mean interval of 13 years between immigration or age 11 and clinical onset, with a minimum of 3 years. This series provides further support for the theses: 1) that MS is primarily an environmental disease acquired after childhood; 2) that acquisition requires prolonged or repeated exposure (here 3 years for these medium-to-high MS risk migrants) followed by a prolonged latent or incubation period between acquisition and symptom onset (here 10 years); and 3) that this disease is most likely a widespread but unknown persistent infection which results in clinical MS in only a small proportion of those affected.

Adolescent↗
PubMed1997

Epidemiology of multiple sclerosis in US veterans: VII. Risk factors for MS.

In previous papers of this series, we explored the epidemiology of MS, examining the effects of race, sex, geography, latitude and climate, migration, age at onset, population ancestry, and individual ethnicity on the risk of MS, using an unusually large cohort of MS cases and pre-illness matched controls comprising US veterans of World War II (WWII) and the Korean Conflict (KC). In this paper, we examine primarily the effect of other factors on the risk of MS in this cohort and their relation to those previously studied. We found here that latitude tier of residence at entry into active duty (EAD), years of education, and socioeconomic class (coded from occupation) were similarly associated with MS risk among white men, black men, and white women. Higher levels of each factor showed increased MS risk. Multivariate analyses indicated that for white male WWII subjects an urban address, 9 or more years of education, uncorrected visual acuity less than 20/20 at EAD, a more northern latitude, and a higher proportion of the subject's EAD state population reporting Swedish ancestry each significantly increased the risk of MS. White male KC subjects showed roughly the same patterns, except that uncorrected visual acuity less than 20/20 was associated with lower MS risk (ancestry/ethnicity was not studied). For black male WWII and KC subjects combined, a similar analysis (omitting ancestry/ethnicity) showed that only latitude at EAD and 9 or more years of education were independently associated with a significantly higher MS risk, and for WWII plus KC white women (also without ancestry/ethnicity), only latitude was a significant risk factor in these multivariate analyses. The smaller number of subjects, especially in these last two groups, limited the power to detect statistically significant risks in these last analyses. Similarities to white men of WWII in univariate analyses for all other groups suggest that findings for the former would otherwise apply to the latter. Although the interpretations of these associations may be obscure, in addition to geography, age, sex, and race, per se, higher socioeconomic status is significantly associated with higher MS risk in black and white men and in white women in the United States.

Black or African American↗
PubMed1997

Multiple sclerosis in the Faroe Islands. 7. Results of a case control questionnaire with multiple controls.

Detailed questionnaires were completed in 1978-79 by 23 of the 28 then known resident Faroese multiple sclerosis (MS) patients and 127 controls. These controls were divided into 69 Group A (patient sibs and other relatives), 37 Group B (matched neighbor controls, their spouses and sibs, plus patient's spouse), and 21 Group C (distant matched controls, spouses, relatives living where MS patients never resided and British troops were not encamped during the war). No differences between cases and controls were found for education, occupation, types of residence, bathing, sanitary or drinking facilities, and nature of house construction or heating. Detailed dietary histories, available for half the subjects, revealed no differences, cases versus controls, for four age periods between age 0 and 30 years, and for 16 specified foodstuffs. Animal exposures showed overall no consistent differences by location or type of animal. There was a tendency to greater exposure to British troops during the war for cases versus Groups A and B but this did not attain statistical significance. Vaccinations for smallpox, tetanus and diphtheria were less common in the MS; no difference was found for other vaccinations. Except for a relative deficit in the cases for rubella and (insignificantly) for measles, mumps and chicken pox, reported illnesses were equally common among all groups. Operations, hospitalizations and injuries did not differentiate the groups, nor did age at menarche for women. Neurologic symptoms were significantly more common in the cases than in the controls.

Adolescent↗
PubMed1996

An introduction to neuroepidemiology.

Neuroepidemiology is the application of the methods of epidemiology to the problems of clinical neurology. After diagnosis, the most basic characterization of a disease is its frequency. This characterization requires ascertainment of case (numerator) within their population at risk (denominator) to provide incidence, prevalence, and mortality rates. Mortality rates come from government publications, and morbidity rates (incidence and prevalence) from specific field surveys. Definition of the course of illness and identification of risk factors for occurrence or course require specific studies and appropriate statistical testing.

Bias↗
PubMed1995

Multiple sclerosis in the Faroe Islands: transmission across four epidemics.

As of 1991 we had ascertained 42 native resident Faroese plus 12 non-resident "migrant" Faroese with clinical onset of MS in this century. The resident series comprised four successive epidemics beginning in 1943 and then at 13-year intervals thereafter, a separation of very high statistical significance (p < 0.00001). We concluded that the first epidemic in the Faroes resulted from the introduction of a specific but unknown infection which we call the "primary MS affection" (PMSA) by occupying British troops during World War II. Clinical neurologic MS (CNMS) is then the rare late sequel of infection with PMSA. The first epidemic defined age of susceptibility to PMSA as age 11 to 45 at onset of exposure. Models of transmission used for the first three epidemics included the need for two years of exposure before PMSA acquisition and limitation of transmissibility of PMSA to age 13 to 26. With these conditions successive cohorts of susceptible Faroese were defined to account for the second and third epidemics, and they also predicted the occurrence of the fourth epidemic. Further consideration of these models suggests transmissibility is even more limited, perhaps to age 20 to 26 or so.

Adolescent↗
PubMed1995

Epidemiology of multiple sclerosis in US veterans. 6. Population ancestry and surname ethnicity as risk factors for multiple sclerosis.

Previously, we studied the effect of population ancestry on the risk of multiple sclerosis (MS) in US veterans of World War II, comparing by state 1980 US census ancestry data with MS case/control ratios. Here, the joint effects of population ancestry and surname-derived ethnicity on MS risk are examined in the same series. Census data are used again to characterize the population ancestry of the state from which each subject entered active duty (EAD)--that is, the proportions of the populace reporting various ancestries--and subjects were also individually categorized into a single ethnic group, without knowledge of case/control status, based on surname. In this study population, categorized ethnicity was strongly correlated with population ancestry, as expected. Although univariate analyses showed statistically significant associations between MS risk and several surname-derived ethnicities and ethnic groups, when residence at EAD was accounted for as well, there was almost no ethnic variation in MS risk. A logistic regression analysis further showed that variations in MS risk are associated most strongly with latitude and population ancestry group; in particular, subjects who entered military service from states with higher proportions of Swedish or French ancestry had higher risks of MS. After adjustment for characteristics of place, the only significant individual ethnicity factor found was Southern European ethnicity. In general, we conclude that an individual's ethnicity seems to be of less relative importance in determining MS risk than is the population ancestry of the state of EAD. These findings underscore the fact that MS is a disease of place, with 'place' including not only attributes of the locale (e.g., latitude), but also of its populace (e.g., ancestry).

Adult↗
PubMed1994

Clinical definition for multiple sclerosis treatment trials.

Clinically, the Schumacher Panel criteria remain the best set of diagnostic criteria. Two subsets therein are definable, i.e., exacerbating-remitting (ER) and chronic progressive (CP), with the latter subdivided into progressive from onset and secondarily progressive. A clinically stable stage can also be recognized. It has been customary in treatment trials to separate ER and CP patients. End point for the latter is a comparison of neurologic status at the end of the trial with that entry. A similar assessment can be made for ER patients. With this criterion both types could be included in a single study. One could also, though, treat the exacerbation in an acute study or assess whether exacerbations can be prevented in a long-term trial. Most clinicians no longer consider monophasic disease as multiple sclerosis (MS). Depending on clinical extent, such patients are divisible into acute disseminated encephalomyelitis, Devic disease, transverse myelopathy, or optic neuritis. Each subgroup could be studied as with an acute exacerbation or in long term as to whether future and different neurologic insults can be prevented. One measure of neurologic status is the Disability Status Scale (DSS), which grades clinical impairment due to MS on a 0 (normal) to 10 (death due to MS) basis. The expanded DSS (EDSS) subdivides each step 1 through 9 into two. Type and severity of neurologic impairment is defined by graded involvement in the following eight functional systems (FS): pyramidal, cerebellar, brainstem, sensory, bowel and bladder, visual, cerebral, and other. Frequency and severity of each FS correlates strongly with DSS scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗