Juha Pekkanen

Confounding and Effect Modification in the Short-term Effects of Ambient Particles on Total Mortality: Results from 29 European Cities within the Aphea2 Project

We present the results of the Air Pollution and Health: A European Approach 2 (APHEA2) project on short-term effects of ambient particles on mortality with emphasis on effect modification. We used daily measurements for particulate matter less than 10 &mgr;m in aerodynamic diameter (PM10) and/or black smoke from 29 European cities. We considered confounding from other pollutants as well as meteorologic and chronologic variables. We investigated several variables describing the cities’ pollution, climate, population, and geography as potential effect modifiers. For the individual city analysis, generalized additive models extending Poisson regression, using a smoother to control for seasonal patterns, were applied. To provide quantitative summaries of the results and explain remaining heterogeneity, we applied second-stage regression models. The estimated increase in the daily number of deaths for all ages for a 10 &mgr;g/m3 increase in daily PM10 or black smoke concentrations was 0.6% [95% confidence interval (CI) = 0.4–0.8%], whereas for the elderly it was slightly higher. We found important effect modification for several of the variables studied. Thus, in a city with low average NO2, the estimated increase in daily mortality for an increase of 10 &mgr;g/m3 in PM10 was 0.19 (95% CI = 0.00–0.41), whereas in a city with high average NO2 it was 0.80% (95% CI = 0.67–0.93%); in a relatively cold climate the corresponding effect was 0.29% (95% CI = 0.16–0.42), whereas in a warm climate it was 0.82% (95% CI = 0.69–0.96); in a city with low standardized mortality rate it was 0.80% (95% CI = 0.65–0.95%), and in one with a high rate it was 0.43% (95% CI = 0.24–0.62). Our results confirm those previously reported on the effects of ambient particles on mortality. Furthermore, they show that the heterogeneity found in the effect parameters among cities reflects real effect modification, which is explained by specific city characteristics.

Serum Total Cholesterol, Apolipoprotein E {FC12}e4 Allele, and Alzheimer’s Disease

The σ4 allele of the apolipoprotein E (apoE) is associated with Alzheimer’s disease (AD) and also with elevated serum total cholesterol and low-density lipoprotein levels. However, the interrelationships between apoE genotype, plasma cholesterol levels and AD risk have been studied very little. We examined the possible role of serum total cholesterol in the pathogenesis of AD in a population-based sample of 444 men, aged 70–89 years, who were survivors of the Finnish cohorts of the Seven Countries Study. Previous high serum cholesterol level (mean level ≥6.5 mmol/l) was a significant predictor of the prevalence of AD (odds ratio = 3.1; 95% confidence interval = 1.2, 8.5) after controlling for age and the presence of apoE σ4 allele. In men who subsequently developed AD the cholesterol level decreased before the clinical manifestations of AD. We conclude that high serum total cholesterol may be an independent risk factor for AD and some of the effect of the apoE σ4 allele on risk of AD might be mediated through high serum cholesterol.

How much asthma is really attributable to atopy

In recent decades it has become routine to describe asthma as an atopic disease. A theoretical paradigm has evolved in which allergen exposure produces atopic sensitisation and continued exposure leads to clinical asthma through the development of airways inflammation, bronchial hyperresponsiveness, and reversible airflow obstruction. As Martinez1 notes, this paradigm has been used with particular insistence with regard to house dust mite allergens,2 3 but other allergens (cat, cockroach, dog) are also believed to be important. The importance of atopy is most widely accepted for asthma in children whereas, among adults, asthma has traditionally been divided into “extrinsic” and “intrinsic” asthma, although this also has been challenged.4 It is acknowledged that not all cases of asthma fit this paradigm—for example, some occupational causes of asthma do not appear to involve atopy—but these are regarded as interesting minor anomalies that do not threaten the dominant paradigm. In this review we assess the extent to which the development of asthma is attributable to atopy (we do not consider the separate issue of the extent to which the development of atopy itself is attributable to allergen exposure, although this is also the subject of debate1). We start by considering definitions of asthma and atopy and then review evidence on their association in random population surveys. We do not intend to argue that atopy does not play an important role in the development of a significant proportion of asthma cases. However, our concern is that the proportion of asthma cases attributable to atopy may have been overestimated, and that other possible aetiological mechanisms and risk factors for asthma may therefore have been neglected. The definition of asthma is still controversial but an appropriate definition is a precondition for addressing the issues considered in this paper. The term “asthma” encompasses a …

Relation of serum homocysteine and lipoprotein(a) concentrations to atherosclerotic disease in a prospective Finnish population based study

The relation of serum total homocysteine and lipoprotein(a) (Lp(a)) with the incidence of atherosclerotic disease was investigated among 7424 men and women aged 40-64 years free of atherosclerotic disease at baseline in 1977. During the 9-year follow-up, 134 male and 131 female cases with either myocardial infarction or stroke were identified. For each case a control subject was selected belonging to the same sex and 5-year age group. Serum samples collected in 1977 were stored at -20 degrees C and analyzed in 1991. The mean serum homocysteine concentration of male cases and controls was 9.99 mumol/l and 9.82 mumol/l at baseline and that of female cases and controls 9.58 mumol/l and 9.24 mumol/l, respectively. The median serum Lp(a) concentration of male cases and controls was 73 mg/l and 108 mg/l and that of female cases and controls 113 mg/l and 91 mg/l, respectively. The differences between cases and controls were not statistically significant. There was also no significant association between either homocysteine or Lp(a) and atherosclerotic disease, myocardial infarction or stroke in logistic regression analyses. The odds ratios varied from 1.00 to 1.26 for homocysteine and from 0.81 to 1.06 for Lp(a). The results of this prospective population-based study do not support the hypotheses that serum homocysteine or Lp(a) are risk factors for atherosclerotic disease. The lack of association between serum homocysteine and atherosclerotic disease may be due to the exceptionally low gene frequency predisposing to homocysteinemia in Finland.

Non-eosinophilic asthma: importance and possible mechanisms

There is increasing evidence that inflammatory mechanisms other than eosinophilic inflammation may be involved in producing the final common pathway of enhanced bronchial reactivity and reversible airflow obstruction that characterises asthma. A review of the literature has shown that, at most, only 50% of asthma cases are attributable to eosinophilic airway inflammation. It is hypothesised that a major proportion of asthma is based on neutrophilic airway inflammation, possibly triggered by environmental exposure to bacterial endotoxin, particulate air pollution, and ozone, as well as viral infections. If there are indeed two (or more) subtypes of asthma, and if non-eosinophilic (neutrophil mediated) asthma is relatively common, this would have major consequences for the treatment and prevention of asthma since most treatment and prevention strategies are now almost entirely focused on allergic/eosinophilic asthma and allergen avoidance measures, respectively. It is therefore important to study the aetiology of asthma further, including the underlying inflammatory profiles.

Dietary factors determining diabetes and impaired glucose tolerance. A 20-year follow-up of the Finnish and Dutch cohorts of the seven countries study.

OBJECTIVE To investigate the role of diet as a predictor of glucose intolerance and non-insulin-dependent diabetes mellitus (NIDDM). RESEARCH DESIGN AND METHODS At the 30-year follow-up survey of the Dutch and Finnish cohorts of the Seven Countries Study, in 1989/1990, men were examined according to a standardized protocol including a 2-h oral glucose tolerance test. Information on habitual food consumption was obtained using the cross-check dietary history method. Those 338 men in whom information on habitual diet was also available 20 years earlier were included in this study. Subjects known as having diabetes in 1989/1990 were excluded from the analyses. RESULTS Adjusting for age and cohort, the intake of total, saturated, and monounsaturated fatty acids and dietary cholesterol 20 years before diagnosis was higher in men with newly diagnosed diabetes in the survey than in men with normal or impaired glucose tolerance. After adjustment for cohort, age, past body mass index, and past energy intake, the past intake of total fat was positively associated with 2-h postload glucose level (P < 0.05). An independent inverse association with the past intake of vitamin C was observed (P < 0.05). These associations were independent of changes in the intake of fat and vitamin C during the 20-year follow-up. An increase in the consumption of vegetables and legumes, potatoes, and fish during the 20-year follow-up was inversely related with 2-h glucose level (P < 0.05). CONCLUSIONS Although the regression coefficients were in general not very large, these results indicate that a high intake of fat, especially that of saturated fatty acids, contributes to the risk of glucose intolerance and NIDDM. Foods such as fish, potatoes, vegetables, and legumes may have a protective effect. In addition, the observed inverse association between vitamin C and glucose intolerance suggests that antioxidants may also play a role in the development of derangements in glucose metabolism.

Changes in risk factors explain changes in mortality from ischaemic heart disease in Finland.

Abstract Objectives: To estimate the extent to which changes in the main coronary risk factors (serum cholesterol concentration, blood pressure, and smoking) explain the decline in mortality from ischaemic heart disease and to evaluate the relative importance of change in each of these risk factors. Design: Predicted changes in ischaemic heart disease mortality were calculated by a ligistic regression model using the risk factor levels assessed by cross sectional population surveys, in 1972, 1977, 1982, 1987, and 1992. These predicted changes were compared with observed changes in mortality statistics. Setting: North Karelia and Kuopio provinces, Finland. Subjects: 14 257 men and 14 786 women aged 30–59 randomly selected from the national population register. Main outcome measures: Levels of the risk factors and predicted and observed changes in mortality from ischaemic heart disease. Results — The observed changes in the risk factors in the population from 1972 to 1992 predicted a decline in mortality from ischaemic heart disease of 44% (95% confidence interval 37% to 50%) in men and 49% (37% to 59%) in women. The observed decline was 55% (51% to 58%) and 68% (61 to 74) respectively. Conclusion: An assessment of the data on the risk factors for ischaemic heart disease and mortality suggests that most of the decline in mortality from ischaemic heart disease can be explained by changes in the three main coronary risk factors.

Body Weight, Cardiovascular Risk Factors, and Coronary Mortality 15-Year Follow-up of Middle-aged Men and Women in Eastern Finland

BACKGROUND Body weight is closely related to several known cardiovascular risk factors, but it may also have an independent effect on the risk of coronary heart disease (CHD). In this study, we analyzed the association between body mass index (BMI) and smoking, serum cholesterol, and blood pressure at baseline, as well as how BMI and the other risk factors are related to CHD mortality. METHODS AND RESULTS A total of 16 113 men and women aged 30 to 59 years were examined in eastern Finland in either 1972 or 1977. Serum cholesterol and blood pressure had a positive association and smoking had a negative association with BMI. During the 15-year prospective follow-up, mortality from CHD was positively associated with BMI. The BMI-associated risk ratio of CHD mortality, adjusted for age and study year, estimated from the Cox proportional hazards model was 1.04 (per kg/m2) (P < .001) among men. Inclusion of smoking in the model increased the risk ratio for BMI, whereas inclusion of serum cholesterol and blood pressure decreased it. In the model that included age, study year, and all three major cardiovascular risk factors, the BMI-associated risk ratio was 1.03 (P = .027). Among women, the BMI-associated risk ratio of CHD mortality adjusted for age and study year was 1.05 (P = .023) and the multifactorial adjusted risk ratio was 1.03 (P = .151). CONCLUSIONS Obesity is an independent risk factor for CHD mortality among men and also contributes to the risk of CHD among women. Part of the BMI-associated risk of CHD mortality is mediated through other known cardiovascular risk factors. By preventing overweight, a substantial part of CHD mortality may be prevented.

Particulate Air Pollution and Risk of ST-Segment Depression During Repeated Submaximal Exercise Tests Among Subjects With Coronary Heart Disease The Exposure and Risk Assessment for Fine and Ultrafine Particles in Ambient Air (ULTRA) Study

Background—Daily variations in ambient particulate air pollution have been associated with cardiovascular mortality and morbidity. We therefore assessed the associations between levels of the 3 main modes of urban aerosol distribution and the occurrence of ST-segment depressions during repeated exercise tests. Methods and Results—Repeated biweekly submaximal exercise tests were performed during 6 months among adult subjects with stable coronary heart disease in Helsinki, Finland. Seventy-two exercise-induced ST-segment depressions >0.1 mV occurred during 342 exercise tests among 45 subjects. Simultaneously, particle mass <2.5 &mgr;m (PM2.5) and the number concentrations of ultrafine particles (particle diameter 10 to 100 nm [NC0.01–0.1]) and accumulation mode particles (100 to 1000 nm [NC0.1–1]) were monitored at a central site. Levels of particulate air pollution 2 days before the clinic visit were significantly associated with increased risk of ST-segment depression during exercise test. The association was most consistent for measures of particles reflecting accumulation mode particles (odds ratio 3.29; 95% CI, 1.57 to 6.92 for NC0.1–1 and 2.84; 95% CI, 1.42 to 5.66 for PM2.5), but ultrafine particles also had an effect (odds ratio 3.14; 95% CI, 1.56 to 6.32), which was independent of PM2.5. Also, gaseous pollutants NO2 and CO were associated with an increased risk for ST-segment depressions. No consistent association was observed for coarse particles. The associations tended to be stronger among subjects who did not use &bgr;-blockers. Conclusions—The present results suggest that the effect of particulate air pollution on cardiovascular morbidity is at least partly mediated through increased susceptibility to myocardial ischemia.

Maternal vitamin D intake during pregnancy is inversely associated with asthma and allergic rhinitis in 5‐year‐old children

Background Vitamin D is known to have a number of immunological effects and it may play a role in preventing allergic diseases.