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N L Valdiviezo

Publications and source records attributed to N L Valdiviezo.

9 recordsLinked to original sources
PubMed1984

Application of simulation techniques for estimating duration of multiple sclerosis derived from prevalence-formed cohorts.

Comparisons of the average duration of multiple sclerosis derived from a prevalence survey of cases alive in 1970 in a low-risk area (Los Angeles County, California) and a high-risk area (King and Pierce Counties, Washington) suggest that patients in the high-risk area had a longer duration of disease than patients in the low-risk area. Because this finding was unexpected and because the underlying population of these two areas has been increasing at different rates, two simulation models were developed to estimate the duration of multiple sclerosis from a prevalence survey, taking into account the effects of changes in the population over time. Comparison of the durations derived from the two simulation studies suggested that underestimation of true backward recurrence time from the simulation studies was similar for the two study areas. Thus, the observed differences in duration between the two areas probably reflect the course of disease rather than differences in rate of growth of the two populations. These studies demonstrate the usefulness of simulation studies in estimating disease duration from cohorts derived from prevalence surveys of non-stable populations.

Adult↗
PubMed1983

Underlying cause of death as recorded for multiple sclerosis patients: associated factors.

The coding of multiple sclerosis (MS) as underlying cause of death (UCD) on the death certificate provides an important epidemiologic resource for both descriptive and analytic studies. However, not all deaths among MS patients will be so coded. We investigated the effect on estimated occurrence of MS and on characteristics of MS patients when only UCD codes are used to identify cases. Of 2329 MS patients living in Los Angeles County (California) or King/Pierce Counties (Washington) in 1970, 438 had died by 1980. Only 53% of the deaths were coded to MS; 47% were attributed to other causes. Based on our comparisons, the use of only MS-coded deaths to describe decedents would: underestimate the age at MS onset; overestimate the female:male ratio; underestimate age at death; and underestimate duration of MS. Also, the percentage of MS-coded deaths decreased with lengthening duration of follow-up of these prevalent cases. The effect of using only UCD codes to report characteristics of decedents with other chronic diseases may well be similar.

Adult↗
PubMed1982

Factors associated with a malignant or benign course of multiple sclerosis.

Eight hundred thirty-four patients with multiple sclerosis (MS) in King and Pierce Counties, Washington, and in Los Angeles County, California, with symptomatic onset between 1960 and 1969 were followed up for disability status in 1980. A higher proportion of the 375 patients who were not walking or deceased in 1980 had a late age of onset, resided in Los Angeles County, had motor or coordination symptoms at onset, and reported adverse responses to heat exposure and favorable responses to cold exposure, whereas a higher proportion of the 299 patients still walking without aids had early onset age and vision, speech, or sensory symptoms, or all three, at onset. The results suggest (1) that both host factors (age at first manifestation of symptoms and types of symptoms at onset) and environmental factors (place of residence and exposure to heat and cold) are determinants of disease course and (2) that most patients with MS should avoid exposure to heat.

Adult↗
PubMed1982

Factors associated with a rapid course of multiple sclerosis.

A cohort of 886 cases of multiple sclerosis (MS) who had onset between Jan 1, 1960, and Dec 31, 1969, and who were resident in 1970 in either a low-prevalence area (Los Angeles County, California, 560 cases) or in a high-prevalence area (King and Pierce Counties, Washington, 326 cases) were followed up for changes in disability status through Dec 31, 1979. Cases had to meet the modified Schumacher criteria for definite/probable MS and to have had a diagnosis of MS or equivalent by a physician. Onset year of disease was determined by onset of the earliest reported symptom. Disability status was determined at intake by an interviewer-administered questionnaire and in subsequent years by an annual mailed questionnaire (self-reported disability status). Progression to a nonambulatory status or death was significantly greater among (1) patients with an older age at onset, (2) patients with a rapid early course, (3) males, and (4) residents of Los Angeles County.

Adult↗
PubMed1981

Mortality in persons with multiple sclerosis in the Seattle and Los Angeles areas.

Case-mortality and survival rates of more than 2,000 prevalent cases of multiple sclerosis (MS) residing in either Los Angeles County, California, or King and Pierce Counties, Washington, and followed up for 105 months, are reported. Case-mortality at the end 105 months was 16.9% of the total group. All age and sex groups had a lower survival rate than the US general population; this difference was especially pronounced in the high-disability groups. There was a trend toward higher case-mortality in high-disability Los Angeles County patients when compared with high-disability patients from King and Pierce Counties.

Adolescent↗
PubMed1981

Relationship between measles HI titers and an MS susceptibility gene.

Recently published studies of formal linkage analyses strongly suggest that a multiple sclerosis susceptibility (MSS) gene is linked to the HLA region of the sixth chromosome. The objective of this analysis was to investigate whether or not the gene has any demonstrable relationship to the immune status with regard to measles within members of multiple-case MS families. Family members were HLA-typed, and levels of antibodies to measles were determined using the hemagglutination inhibition assay. Since a specific, HLA-defined haplotype within each family is presumably a marker for the MSS gene, family members were characterized as either carrying [(+) controls] or not carrying [(-) controls] the MSS gene by the presence of this specific haplotype. Twenty families were entered into the analyses. Results revealed that the mean titer to measles was not different between (+) and (-) controls, and that MS cases had significantly higher titers than both control groups combined.

Age Factors↗
PubMed1981

Two populations with multiple sclerosis. Clinical and demographic characteristics.

Cross-sectional data from 1,793 cases of definite or probable multiple sclerosis (MS) identified in an extensive population survey in King and Pierce (K-P) Counties, Washington and Los Angeles (LA) County, California, were analyzed. Compared to the U.S. population as a whole, patients were more likely to be divorced and to have more years of schooling. The prevalence of MS was higher for females, and for northern-born, regardless of sex. Reconstructed age-, sex-specific incidence rate estimates for natives of the two areas showed a much higher peak annual incidence occurring in an older age group in K-P than in LA. Earliest symptoms in both areas were numbness in the legs, double vision, and loss of vision in one or both eyes. Weakness in arms, speech difficulties, and urinary incontinence tended to be late symptoms. The overall assessment of disability levels showed more than half of the patients to be fully ambulatory at the time of the first interview, with a somewhat higher proportion of each sex severely disabled in California. The ages of onset tended to be younger in LA than in K-P. The earlier onset of disease and the higher proportion of patients with high disability in Los Angeles County suggest that the course of disease is more malignant in this low-prevalence area.

Adolescent↗
PubMed1981

Similar levels of immune complexes in cases of multiple sclerosis and their unaffected relatives.

To investigate the possible effect of the hypothetical multiple sclerosis susceptibility (MSS) gene on circulating immune complexes, we employed a sensitive assay to test for the presence of immune complexes in sera of MS patients and unaffected relatives classified by the presence/absence of HLA-defined markers for the MSS gene. We found no significant differences between cases and relatives. The results suggest that elevated immune complex levels in MS patients' sera reported by others may not be unique to MS cases, but may represent instead a familial phenomenon. We also report a possible association between the A3 + B7 haplotype and increased immune complexes.

Antigen-Antibody Complex↗