Objective To explore the importance of early life factors shared by siblings, such as parental socioeconomic position, parental practices, housing and neighbourhood, for the association between cardiovascular disease (CVD) risk factors and mortality from CVD, ischaemic heart disease (IHD) and cerebrovascular disease.
Methods Norwegian health surveys (1974–2003) were linked with data from the Norwegian Family Based Life Course Study and the Cause of Death Registry. Participants with at least one full sibling among survey participants (n=2 71 643) were included. Data on CVD risk factors, body mass index (BMI), height, systolic blood pressure (SBP) and total cholesterol (TC) were stratified into ‘low’, ‘medium’ and ‘high’ risk, and smoking to ‘daily smoking’ and ‘not daily smoking’.
Results Mean age of participants was 41 years, mean follow-up time was 19 years and during follow-up 2512 died from CVD. For each category of increased risk factor level, the per step HR of CVD mortality was increased by 1.91 (95% CI 1.78 to 2.05) for SBP, 1.67 (1.58 to 1.76) for TC, 1.44 (1.36 to 1.53) for BMI, 1.26 (1.18 to 1.35) for height and 2.89 (2.66 to 3.14) for smoking. In analyses where each sibship (groups of full siblings) had a group-specific baseline hazard, these associations were attenuated to 1.74, 1.51, 1.29, 1.18 and 2.63, respectively. The associations between risk factors and IHD mortality followed the same pattern.
Conclusion Early life family factors explained a small part of the association between risk factors and mortality from CVD and IHD in a relatively young sample.
- risk factors
- public health
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Contributors ØN conceived the idea for the article. MKRK did the statistical analyses and the drafting of the article. All authors contributed in the final stage of the writing.
Funding The work was supported by the Norwegian Research Council (grant number 213788).
Competing interests None declared.
Patient consent New consent is not required as consent was obtained at the time the data was collected and by those who undertook the study.
Ethics approval Norwegian Regional Committees for Medical and Health Research Ethics (REK) (2012/827).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Data are owned by Norwegian Institute of Public Health (NIPH) and cannot be shared. Application has to be sent to NIPH after approval of study from Norwegian Regional Committees for Medical and Health Research Ethics.
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