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.

Background: Tuberculosis notification rates for London have risen dramatically in recent years. Molecular typing of Mycobacterium tuberculosis has contributed to our understanding of the epidemiology of tuberculosis throughout the world. This study aimed to assess the degree of recent transmission of M tuberculosis in London and subpopulations of the community with high rates of recent transmission. Methods: M tuberculosis isolates from all persons from Greater London diagnosed with culture positive tuberculosis between 1 July 1995 and 31 December 1997 were genetically fingerprinted using IS6110 restriction fragment length polymorphism (RFLP) typing. A structured proforma was used during record review of cases of culture confirmed tuberculosis. Cluster analysis was performed and risk factors for clustering were examined in a univariate analysis followed by a logistic regression analysis with membership of a cluster as the outcome variable. Results: RFLP patterns were obtained for 2042 isolates with more than four copies of IS6110; 463 (22.7%) belonged to 169 molecular clusters, which ranged in size from two (65% of clusters) to 12 persons. The estimated rate of recent transmission was 14.4%. Young age (0-19 years) (odds ratio (OR) 2.65, 95% confidence interval (CI) 1.59 to 4.44), birth in the UK (OR 1.55, 95% CI 1.04 to 2.03), black Caribbean ethnic group (OR 2.19, 95% CI 1.15 to 4.16), alcohol dependence (OR 2.33, 95% CI 1.46 to 3.72), and streptomycin resistance (OR 1.82, 95% CI 1.15 to 2.88) were independently associated with an increased risk of clustering. Conclusions: Tuberculosis in London is largely caused by reactivation or importation of infection by recent immigrants. Newly acquired infection is also common among people with recognised risk factors. Preventative interventions and early diagnosis of immigrants from areas with a high incidence of tuberculosis, together with thorough contact tracing and monitoring of treatment outcome among all cases of tuberculosis (especially in groups at higher risk of recent infection), remains most important.

Background -In a previous retrospective study of tuberculosis in south London among Asian immigrants from the Indian subcontinent Hindu Asians were found to have a significantly increased risk for tuberculosis compared with Muslims. This finding has been further investigated by examining the role of socioeconomic and lifestyle variables, including diet, as risk factors for tuberculosis in Asian immigrants from the Indian subcontinent resident in south London. Methods -Using a case-control study technique Asian immigrants from the Indian subcontinent diagnosed with tuberculosis during the past 10 years and two Asian control groups (community and outpatient clinic controls) from the Indian subcontinent were investigated. Cases and community controls were approached by letter. A structured questionnaire concerning a range of demographic, migration, socioeconomic, dietary, and health topics was administered by a single trained interviewer to subjects (56 cases and 100 controls) who agreed to participate. Results -The results confirmed earlier findings that Hindu Asians had an increased risk oftuberculosis compared with Muslims. However, further analysis revealed that religion had no independent influence after adjustment for vegetarianism (common among Hindu Asians). Unadjusted odds ratios for tuberculosis among vegetarians were 2-7 (95% CI 1-1 to 6.4) using community controls, and 4-3 (95% CI 1-8 to 10.4) using clinic controls. There was a trend of increasing risk of tuberculosis with decreasing frequency of meat or fish consumption. Lactovegetarians had an 85 fold risk (95% CI 1-6 to 45.4) compared with daily meat/ fish eaters. Adjustment for a range ofother socioeconomic, migration, and lifestyle variables made little difference to the relative risks derived using either community or clinic controls. Conclusions -These results indicate that a vegetarian diet is an independent risk factor for tuberculosis in immigrant Asians. The mechanism is unexplained. However, vitamin D deficiency, common among vegetarian Asians in south London, is known to affect immunological competence. Decreased immunocompetence associated with a vegetarian diet might result in increased mycobacterial reactivation among Asians from the Indian subcontinent.

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