Survival advantage of cohort participation attenuates over time: results from three long-standing community-based studies.

PURPOSE: Cohort participants usually have lower mortality rates than nonparticipants, but it is unclear if this survival advantage decreases or increases as cohort studies age. METHODS: We used a 1975 private census of Washington County, Maryland, to compare mortality among cohort participants to nonparticipants for three cohorts, Campaign Against Cancer and Stroke (CLUE I), Campaign Against Cancer and Heart Disease (CLUE II), and Atherosclerosis Risk In Communities (ARIC) initiated in 1974, 1989, and 1986, respectively. We analyzed mortality risk using time-truncated Cox regression models. RESULTS: Participants had lower mortality risk in the first 10 years of follow-up compared with nonparticipants (fully adjusted average hazard ratio [95% confidence intervals] were 0.72 [0.68, 0.77] in CLUE I, 0.69 [0.65, 0.73] in CLUE II, and 0.74 [0.63, 0.86] in ARIC), which persisted over 20 years of follow-up (0.81 [0.78, 0.84] in CLUE I, 0.87 [0.84, 0.91] in CLUE II, and 0.90 [0.83, 0.97] in ARIC). This lower average hazard for mortality among participants compared with nonparticipants attenuated with longer follow-up (0.99 [0.96, 1.01] after 30+ years in CLUE I, 1.02 [0.99, 1.05] after 30 years in CLUE II, and 0.95 [0.89, 1.00] after 30+ years in ARIC). In ARIC, participants who did not attend visits had higher mortality, but those who did attend visits had similar mortality to the community. CONCLUSIONS: Our results suggest the volunteer selection for mortality in long-standing epidemiologic cohort studies often diminishes as the cohort ages.

Subclinical nephritis in South Trinidad

Incidental urines from 2019 members of the family households of 369 patients hospitalized wih acute glomerulonephritis, 1605 residents of a village, and 1299 school-children were tested with Hema-Combistix. (In this report, the family of a patient is termed a nephritis family.) Hematuria was more frequent in nephritis family members under 10 years old than in similiar control subjects. Proteinuria was more frequent in nephritis family members aged 10 to 30 and 40 to 60 years than in similiar village residents. The control school-children (tested at school) had proteinuria more frequently than did nephritis family children (tested at home). Urine abnormalities were found in 219 of the nephritis family members. Subtracting similiar urine abnormalities found in the control groups from those of the nephritis family members leaves 98 of these abnormalities presumably attributed to family asociation with currently hospitalized cases of acute nephritis. Serum á-1-C gloulin was decreased in 16 of the nephritis family members with urine abnormalities and in only one of 207 subjects from the control groups. Decreased serum á-1-C globulin was associated with mild stigmata of acute glomerulonephritis in the nephritis family members (AU)

Changing types of nephritogenic streptococci in Trinidad

The relation of seven different M types of streptococci to acute glomerulonephritis associated with skin lesions in South Trinidad has been studied by means of type-specific antibody assays as well as by isolation and identification of the strains. The data indicate that, one after another, five of these strains have prevailed among patients with acute glomerulonephritis during the past five years. At least three of the strains (M-types 55,49,57, and/or 60) were associated with epidemic increases in nephritis cases. The appearance of five consecutively predominant types of nephritogenic streptococci during a relatively short period of time is in contrast to the continuing prevalence of M-type 12 strains among nephritogenic streptococci primarily associated with respiratory infections in temperate zones. These observations suggest that the skin sores commonly found on children in tropical Trinidad, provide a particularly suitable environment for development of nephritogenic types. It remains to be seen whether these types will recur or whether new types will continue to emerge in Trinidad. (AU)

Streptococcal strains associated with different phases of epidemic acute nephritis in Trinidad

We will present bacteriological evidence for an association of acute glomerulonephritis with several streptococcal strains isolated from skin lesions in Trinidad; Types 52 and 55 during the first wave and type 49 during the second wave of the 1964-65 epidemic; atypical "type 2" in a sub-epidemic rise in cases during an endemic year; type 57 during a subsequent epidemic period; and type 60 most recently. Immunological confirmation of association of these strains with acute glomerulonephritis was obtained only for type 55. Low incidence of serum type specific antibodies to types 49 and "type 2" may be attribued to their poor antigenicity. However, this is not the case with type 57. Emergence of at least five and perhaps six apparently new types of nephritogenic streptococci during a relatively short period suggests that each recurrent epidemic wave of acute nephritis is the result of a newly introduced or newly developed strain of nephritogenic streptococci. Several questions might be asked: From where do these different types come?. Are they brought into Trinidad from outside or do they represent local mutants? Does a skin infection represent a particularly suitable environment for development of new streptococcal antigens? (AU)

Streptococcal skin infections and epidemic acute nephritis in Trinidad

We have presented bacteriological evidence for an association of acute glomerulonephritis with several streptococcal strains isolated from skin lesions in Trinidad: Types 52 and 55 during the first wave and type 49 during the second wave of the 1964-65 epidemic; atypical "type 2" in a sub-epidemic rise in cases during an endemic year; type 57 during a subsequent epidemic period; and type 60 most recently. Immunological confirmation of association of these strains with acute glomerulonephritis was obtained only for type 55. Low incidence of serum type specific antibodies to types 49 and "type 2" may be attributed to their poor antigenicity. However, this is not the case with type 57. Emergence of at least five and perhaps six apparently new types of nephritogenic streptococci during a relatively short period suggests that each recurrent epidemic wave of acute nephritis is the result of a newly introduced or newly developed strain of nephritogenic streptococci. Several questions might be asked: From where do these different types come? Does a skin infection represent a particularly suitable environment for development of new streptococcal antigens? (Summary)

Urinary abnormalities in families of patients with acute glomerulonephritis - abstract

A study was undertaken to estimate the frequency of subclinical glomerulonephritis in the families of patients admitted with acute glomerulonephritis to San Fernando General Hospital. The findings are expected to bear on the question of the etiology of cases of prolifertive diffuse chronic glomerulonephritis where no history is found of an acute episode. One thousand five hundred members of immediate families of patients admitted during the past year were visited within 31 days of the admission. Incidental urines in 10 percent had hematuria or proteinuria by Hemacomistix. These were examined weekly and had urinalyses, urine, throat, and skin cultures and Beta-1-C globulin and ASO determinations. For comparison 1,300 children aged 5-14 from four South Trinidad schools were tested. All with urinary abnormalities and an equal number of controls had urines repeated and Beta-1-C determinations. No school children had clinically manifest nephritis. Among nephritis family school aged children with urinary abnormalities, none were hypertensive, and edema or low complement was uncommon. The proportion of the remainder whose urinary abnormalities can be attributed to nephritis is estimated by comparing with age-specific and type of abnormality specific rates in the control school children. Hematuria was enough more common in nephritis family children that it can usually be attributed to nephritis. The subclinical: clinical case ratio ascertained this way in immediate families in South Trinidad would seem to be less than 1:1(AU)