The effect of C. burnetii infection on the quality of life of patients following an outbreak of Q fever.

Sixty-six cases of Q fever were diagnosed in people affiliated with a goat-farming co-operative in rural Newfoundland in the spring of 1999. Follow-up studies which included administration of the Short Form 36 Health Survey (SF-36) were conducted 3 and 27 months after the initial outbreak to prospectively follow the effects of acute Q fever on the quality of life of the participants. Twenty-seven months after the outbreak 51% of those who had Q fever reported persistent symptoms including seven participants whose symptoms had initially resolved 3 months after the outbreak. Individuals with Q fever had significantly lower scores on five of the eight scales in the SF-36 and lower scores in the mental and physical summary scales compared to uninfected controls. Although this supports the hypothesis of a 'post Q fever fatigue syndrome' (QFFS), further study is warranted.

Accurate partition of individuals into full-sib families from genetic data without parental information.

Two Markov chain Monte Carlo algorithms are proposed that allow the partitioning of individuals into full-sib groups using single-locus genetic marker data when no parental information is available. These algorithms present a method of moving through the sibship configuration space and locating the configuration that maximizes an overall score on the basis of pairwise likelihood ratios of being full-sib or unrelated or maximizes the full joint likelihood of the proposed family structure. Using these methods, up to 757 out of 759 Atlantic salmon were correctly classified into 12 full-sib families of unequal size using four microsatellite markers. Large-scale simulations were performed to assess the sensitivity of the procedures to the number of loci and number of alleles per locus, the allelic distribution type, the distribution of families, and the independent knowledge of population allelic frequencies. The number of loci and the number of alleles per locus had the most impact on accuracy. Very good accuracy can be obtained with as few as four loci when they have at least eight alleles. Accuracy decreases when using allelic frequencies estimated in small target samples with skewed family distributions with the pairwise likelihood approach. We present an iterative approach that partly corrects that problem. The full likelihood approach is less sensitive to the precision of allelic frequencies estimates but did not perform as well with the large data set or when little information was available (e.g., four loci with four alleles).

Sleep disturbances and mortality: results from the Canadian Study of Health and Aging.

OBJECTIVES: To cross-validate, in a secondary analysis, the observation that daytime sleepiness is associated with an increased risk of death. DESIGN: Prospective cohort study. SETTING: Canada, a nationally representative sample of people age 65 and older. PARTICIPANTS: Nine thousand and eight community-dwelling participants in the Canadian Study of Health and Aging. EXPOSURES: self-reported sleep disturbances. OUTCOMES: Cox hazard ratios (HRs) for death. RESULTS: The unadjusted analysis showed a small increased risk of death from daytime sleepiness (HR = 1.89; 95% confidence interval (CI) = 1.44-2.46), but this finding did not persist in a multivariate model adjusted for age, depression, cognition, comorbid illness, and function. CONCLUSION: Daytime sleepiness itself is not associated with an increased risk of death when other factors are taken into account. Daytime sleepiness may be a proxy for other morbid conditions and therefore for overall tiredness.

Assessing hypertension in the Canadian Study of Health and Aging.

We investigated the self-report hypertension variables in the CSHA, recorded in the screening questionnaire and the Self-Administered Risk Factor (SARF) questionnaire. The two questions showed high agreement (phi coefficient 0.83). Each was modestly but significantly associated with other simultaneous reports of heart disease and stroke, and with subsequent mortality. Only the SARF asked questions about treatment; controlling for treatment effects, five-year survival was longest among those with no hypertension and no treatment (mean survival time 1,645 days; 95% CI 1,632 to 1,658), and shortest for those with no reported hypertension who were receiving "antihypertensive" medications presumably prescribed for other cardiovascular disease (mean survival time 1,496 days; 95% CI 1,457 to 1,535). The SARF questions incorporating high blood pressure and treatment appear preferable to assess the risks associated with hypertension.

Reliability and validity of questions about exercise in the Canadian Study of Health and Aging.

Regular exercise in elderly people has beneficial health effects. We examined exercise frequency and intensity from the Canadian Study of Health and Aging Risk Factor Questionnaire (RFQ). The reliability and validity of these two questions individually, and when combined to form a scale, are reported. Agreement between the self-administered RFQ and an interviewer-administered Add-on Study was examined using intraclass correlations, which were 0.80 for frequency (95% CI 0.77-0.82, p < .001) and 0.75 for intensity (95% CI 0.71-0.78, p = .012). Individuals reporting high levels of exercise frequency, intensity, and a combination of the two showed a smaller proportion of adverse health markers than those reporting no regular exercise. Predictive validity assessed by Cox proportional hazards modeling of mortality showed that the high and moderate levels of frequency, intensity, and combined exercise groups differed significantly (all p < .001) from the no exercise group. We have found that these exercise questions, though simple, appear reliable and valid. The finding that even comparatively crude exercise questions can demonstrate an important relationship to death suggests that the signal for exercise is a strong one, and future studies should seek to better examine mechanisms by which exercise benefit is conferred.