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Biomedical subjects

Mark S Clements

Publications and source records attributed to Mark S Clements.

7 recordsLinked to original sources
PubMed2007

Differential impacts of health care in Australia: trend analysis of socioeconomic inequalities in avoidable mortality.

BACKGROUND: Recent avoidable mortality trends in Australia suggest that health care has made a substantial contribution to reducing mortality. This study investigates if the benefits of health care have been distributed equally by comparing declines in avoidable with non-avoidable mortality over time by socioeconomic status (SES). METHODS: We calculated avoidable and non-avoidable mortality rates in Australia by small areas for 1986, 1991, 1997 and 2002. We performed pooled cross-sectional trend analysis of indirectly standardized mortality rates by SES and year, modelling using Poisson regression with over-dispersion. Socioeconomic inequalities were quantified using the relative (RII) and slope (SII) index of inequality. RESULTS: The annual percentage decline in avoidable mortality at the higher end of the socioeconomic continuum (5.0%; 95% CI: 4.7-5.4%) was larger than at the lower end (3.5%; 3.2-3.8%), with increasing relative inequality between 1986 (RII = 1.54; 1.46-1.63) and 2002 (RII = 2.00; 1.95-2.06), greater than that in non-avoidable mortality (P = 0.036). In absolute terms, avoidable deaths fell annually by 7.4 (6.9-7.8) and 8.4 (7.9-8.9) deaths per 100 000 at the higher and lower end of the spectrum, respectively, with absolute inequality decreasing between 1986 (SII = 97.8; 87.6-107.9) and 2002 (SII = 81.5; 74.6-88.5). CONCLUSIONS: Health care has contributed to decreasing the absolute SES mortality gap. However, advantaged people have obtained a disproportionate benefit of health care, contributing to widening relative health inequalities. A universal heath care system does not guarantee equality in health-care-related outcomes.

Australia↗
PubMed2005

Lung cancer rate predictions using generalized additive models.

Predictions of lung cancer incidence and mortality are necessary for planning public health programs and clinical services. It is proposed that generalized additive models (GAMs) are practical for cancer rate prediction. Smooth equivalents for classical age-period, age-cohort, and age-period-cohort models are available using one-dimensional smoothing splines. We also propose using two-dimensional smoothing splines for age and period. Variance estimation can be based on the bootstrap. To assess predictive performance, we compared the models with a Bayesian age-period-cohort model. Model comparison used cross-validation and measures of predictive performance for recent predictions. The models were applied to data from the World Health Organization Mortality Database for females in five countries. Model choice between the age-period-cohort models and the two-dimensional models was equivocal with respect to cross-validation, while the two-dimensional GAMs had very good predictive performance. The Bayesian model performed poorly due to imprecise predictions and the assumption of linearity outside of observed data. In summary, the two-dimensional GAM performed well. The GAMs make the important prediction that female lung cancer rates in these countries will be stable or begin to decline in the future.

Adult↗
PubMed2005

Control strategies for Q fever based on results of pre-vaccination screening in Victoria, 1988 to 2001.

OBJECTIVE: Data from Q fever pre-vaccination screening were analysed to determine the level of agreement between the two tests of immunity and between disease or vaccination history and immunity, trends in proportion of participants immune to Q fever, and the annual risk of infection. METHOD: Data from nearly 10,000 screening episodes between July 1988 and June 2001 on Victorian workers at high risk were assessed. RESULTS: Most participants were male (86%) and employed in Victorian abattoirs (81%). Agreement between results of tests for immunity was 'fair' (kappa=0.52). Self-reported history of vaccination or infection was a poor predictor of immunity. The proportion of positive blood and skin tests increased with years of exposure to animals/meat, but decreased over the 13-year period with shorter exposures. Hence the percentage requiring vaccination increased from 50% in 1998 to 90% in 2001. The average annual risk of infection among abattoir workers was 45.0 per 1,000 (95% CI 42.3-47.6), and 62.6 per 1,000 (95% CI 57.5-67.7) over the first 10 years of exposure. CONCLUSIONS: This is the first Australian study to estimate the annual risk of Q fever infection in abattoir workers. The study confirmed previous findings of poor agreement between screening tests and predictive value of history of vaccination/ exposure. Up to 90% of new entrants in high-risk workplaces will be susceptible to Q fever and require vaccination. IMPLICATIONS: Systematic post-marketing surveillance is needed to monitor adverse events to the vaccine, duration of protection and possible reasons for vaccine failures.

Adolescent↗
PubMed2005

The health effects of jobs: status, working conditions, or both?

BACKGROUND: This study investigates whether the association of job strain and insecurity with health differs by status. METHODS: A cross-sectional study of 2,249 employed workers aged 40-44 years conducted in two regions in south-east Australia in 2000 used a self-completed questionnaire to collect data. Multivariate analyses were used to compare depression, anxiety, physical health and general practitioner (GP) visits over 12 months across categories of job strain and insecurity for three status groups (high, middle and low). RESULTS: High job strain and job insecurity were independently associated with poor mental health, poor physical health and visits to the GP for all status groups when adjusted for confounders. High job strain was associated with depression (OR = 2.46, 95% CI 1.96-3.07), anxiety (OR = 2.56, 95% Cl 2.05-3.20), lower mean physical health scores (-1.11, 95% CI -1.98 - -0.23), and more visits to the GP (IRR = 1.20, 95% CI 1.05-1.37). High job insecurity also showed significant associations with depression (OR = 3.03, 95% Cl 2.03-4.53), anxiety (OR = 2.66, 95% CI 1.81-3.91), and GP visits (IRR = 1.27, 95% CI 1.01-1.60). There were no significant differences by status in the associations of job strain and insecurity with outcomes. CONCLUSION: High-status workers were just as likely as low-status workers to be exposed to adverse work conditions and both status groups showed similar health effects. IMPLICATIONS: Exposure to insecure and high-strain jobs is likely to rise as economies and labour markets respond to globalisation and political change. High status may not protect employees from either exposure or impact, thus widening the population health consequences of adverse work conditions.

Adult↗
PubMed2005

Multistage carcinogenesis and lung cancer mortality in three cohorts.

Experimental evidence indicates that tobacco smoke acts both as an initiator and a promoter in lung carcinogenesis. We used the two-stage clonal expansion model incorporating the ideas of initiation, promotion, and malignant conversion to analyze lung cancer mortality in three large cohorts, the British Doctors' cohort and the two American Cancer Society cohorts, to determine how smoking habits influence age-specific lung cancer rates via these mechanisms. Likelihood ratio tests indicate that smoking-related promotion is the dominant model mechanism associated with lung cancer mortality in all cohorts. Smoking-related initiation is less important than promotion but interacts synergistically with it. Although no information on ex-smokers is available in these data, the model with estimated variables can be used to project risks among ex-smokers. These projected risks are in good agreement with the risk among ex-smokers derived from other studies. We present 10-year projected risks for current and former smokers adjusted for competing causes of mortality. The importance of smoking duration on lung cancer risk in these cohorts is a direct consequence of promotion. Intervention and treatment strategies should focus on promotion as the primary etiologic mechanism in lung carcinogenesis.

Adult↗
PubMed2004

Modeling trends in HIV incidence among homosexual men in Australia 1995-2006.

BACKGROUND: Previous mathematical models have indicated that any decrease in HIV incidence in homosexual men due to decreased infectiousness from antiretroviral treatment (ARV) may be offset by modest increases in unsafe sex. The aims of this study were to assess the effects of ARV use and increasing unprotected anal intercourse with casual partners (UAIC) in homosexual men on HIV incidence during 1995-2001 and to project HIV incidence depending on trends in ARV use and UAIC. METHODS: A mathematical model of HIV transmission among homosexual men in Australia was developed. HIV incidence during 1995-2001 was estimated assuming that 70% of men in whom HIV was diagnosed received ARVs and assuming a 10% annual increase in UAIC. For 2001-2006, scenarios included ARV levels remaining at 70% or declining to 50% by 2006, combined with UAIC levels remaining at the 2001 level or continuing to increase annually by 10%. FINDINGS: The number of incident HIV cases per year was predicted to have declined during 1996-1998 due to the introduction of effective ARVs, with a slow increase during 1998-2001 due to increased levels of UAIC when use of therapies was fairly stable. From 2001, a continued increase in UAIC was predicted to lead to a rise in HIV incidence. A rise in UAIC combined with a moderate decline in ARV use could lead to a 50% increase in HIV incidence by 2006. INTERPRETATION: These models suggest that widespread ARV use has had some effect in reducing HIV incidence among homosexual men in Australia. However, if current trends in UAIC and ARV use continue, a resurgent HIV epidemic is predicted.

Anti-Retroviral Agents↗