Background -In Western societies there is a winter peak in mortality, largely accounted for by respiratory and cardiovascular deaths. In view of the known seasonal variation in vitamin D, and of the postulated link between tuberculosis and vitamin D deficiency, a study was undertaken to examine whether the presentation of tuberculosis had the same seasonal rhythm as other pulmonary infections. Methods -Using cosinor analysis the presence or absence of seasonality was determined for 57 313 tuberculosis notifications for England and Wales. OPCS data in four weekly notifications over a 10 year period were examined as two quinquential sets (1983-7 and 1988-92 (Thorax 1996;51:944-946)

Objective-To determine whether Helicobacter pyloni, a chronic bacterial infection often acquired in childhood, is associated with increased risk of coronary heart disease and stroke later in life. Design-Nested case-control study. Setting-Prospective study of cardiovascular disease in men aged 40-59 years at entry (1978-1980) (Heart 1996;75:568-572) Keywords: coronary heart disease; Helicobacter pylori; stroke Factors acting early in life may influence adult risk of coronary heart disease,1 2 and play a part in determining its social class distribution.3 Helicobacterpylori (Hpylon) is a chronic bacterial infection which is usually acquired in childhood, particularly in socially deprived circumstances.45 Its associations with peptic ulcer disease and gastric cancer are well recognised -8; both of these conditions are associated with coronary heart disease.9 10 A recent case-control study based on prevalent coronary heart disease in middle aged men provided some support for the possibility of an association between H pylon and coronary heart disease." However, selection biases could not be excluded in that study, and only limited information was available on potential confounding factors. The problems of selection bias were addressed in a further crosssectional study in south London men, which found a strong relation between H pylon seropositivity and electrocardiographic abnormalities suggestive of myocardial ischaemia or infarction, independent of a wide range of confounding variables.'2 However, no study has yet prospectively investigated the relation between H pylon infection and coronary heart disease. We have used a nested case-control study based on a longitudinal study of cardiovascular disease in middle aged men to examine the relation between H pylon seropositivity and subsequent coronary heart disease and stroke.

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(Accepted 10 February 1999)Relation of Chlamydia pneumoniae serology to mortality and incidence of ischaemic heart disease over 13 years in the Caerphilly prospective heart disease study AbstractObjectives To investigate the effect of Chlamydia pneumoniae infection on future development of ischaemic heart disease and mortality. Design Prospective longitudinal study. Setting Caerphilly, South Wales. Subjects Plasma specimens were collected during 1979-83 from 1773 men aged 45-59 years. These were tested for IgG and IgA antibodies to C pneumoniae (TW183) by microimmunofluorescence. Outcome measures 13 year mortality and incident ischaemic heart disease events were ascertained from death certificates, hospital records, and electrocardiographic changes at follow up every 4 to 5 years.Results 642 men (36.2%) had IgG antibodies at a titre of >1 in 16, of whom 362 (20.4% of all men) also had detectable IgA antibodies. The prevalence of ischaemic heart disease (a history of past or current disease) at entry was similar at all IgG antibody titres but was positively related to IgA antibody titre. IgA antibody titre was positively correlated with plasma viscosity but not with other cardiovascular risk factors.