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Serum sodium concentration and risk of stroke in middle-aged males
G Wannamethee1, P H Whincup, A G Shaper
1Department of Public Health, Royal Free Hospital, School of Medicine, London, UK.
Insights
Serum sodium levels impact stroke risk. Optimal levels may reduce stroke risk by over 70%, while very low levels increase mortality. This study highlights the importance of normal sodium ranges for cerebrovascular health.
Area of Science:
- Neurology
- Cardiology
- Epidemiology
Background:
- Cerebrovascular disease is linked to sodium concentration disturbances.
- Understanding the relationship between serum sodium and cardiovascular events is crucial.
Purpose of the Study:
- To investigate the association between serum sodium levels and the risk of stroke and ischaemic heart disease.
- To determine if serum sodium concentration influences cerebrovascular and cardiovascular event risk.
Main Methods:
- A prospective study of 7690 middle-aged males over 9.5 years.
- Analysis of serum sodium levels and incidence of stroke and ischaemic heart disease.
- Statistical adjustments for various cardiovascular risk factors.
Main Results:
- A significant inverse relationship between serum sodium and stroke risk was observed up to 144 mmol/l.
- Levels of 143-144 mmol/l were associated with a >70% reduced stroke risk compared to levels ≤140 mmol/l.
- Increased all-cause and non-cardiovascular mortality were noted at serum sodium levels ≤138 mmol/l, potentially linked to hyponatraemia and lung cancer.
Conclusions:
- Serum sodium concentration may influence stroke risk even within the conventionally normal range.
- Maintaining optimal serum sodium levels could be a strategy for stroke prevention.
- Hyponatraemia is associated with increased mortality, possibly due to underlying conditions like lung cancer.
Background And Methods:
Clinical disturbances of the circulating sodium concentration are both a cause and a consequence of cerebrovascular disease. We examined the relationship between serum sodium level and risk of stroke and major ischaemic heart disease in a prospective study of 7690 middle-aged males drawn from general practices in 24 British towns followed over a 9.5-year period.
Results:
The mean serum sodium level was 141.5 mmol/l and 375 males on antihypertensive treatment were excluded from the analyses. A significant inverse trend was seen between serum sodium and risk of stroke up to 144 mmol/l; above this the risk of stroke was increased. Those with levels of 143-144 mmol/l showed over a 70% reduction in risk of stroke compared with those with levels of < or = 140 mmol/l. The inverse relationship between sodium and stroke up to 144 mmol/l was seen in males with and without pre-existing ischaemic heart disease or stroke, in normotensives and untreated hypertensives, and in non-smokers and current smokers. A weak but significant inverse association was seen between serum sodium and diastolic but not systolic blood pressure. The association between serum sodium level and stroke remained significant after adjustment for diastolic blood pressure and other factors associated with stroke: age, smoking, social class, body mass index, physical activity, heavy drinking, presence of diabetes, blood glucose and pre-existing ischaemic heart disease. No association was seen between serum sodium level and risk of ischaemic heart disease after adjustment for other risk factors. All-cause and non-cardiovascular mortality were significantly increased at serum sodium levels of < or = 138 mmol/l, probably due to an association between lung cancer and hyponatraemia.
Conclusion:
These findings suggest that sodium concentration may be related to risk of stroke even at levels of sodium usually regarded as normal.