Homoarginine and mortality in an older population: the Hoorn study.
BACKGROUND
Homoarginine is an amino acid that may be involved in nitric oxide and energy metabolism. Previous studies in patient populations showed that low homoarginine levels indicate an increased risk of mortality and cardiovascular disease. We evaluated whether low plasma levels of homoarginine are associated with elevated, overall and cause-specific mortality.


MATERIALS AND METHODS
The Hoorn study is a population-based study among older men and women. We calculated Cox proportional hazard ratios (HRs) for overall and cause-specific mortality according to sex-specific homoarginine quartiles.


RESULTS
We included 606 study participants (51·3% women; 70·0 ± 6·6 years). Homoarginine concentrations were higher in men (1·63 ± 0·51 μM), compared with women (1·30 ± 0·44 μM; P < 0·001). After a median follow-up time of 7·8 years, 112 study participants died, including 31 deaths due to cardiovascular diseases and 30 due to cancer. Associations between homoarginine levels and mortality showed a threshold effect with a significant risk increase from the second to the first quartile. Compared with the upper three quartiles, the age-, sex- and BMI-adjusted HR (with 95% CI) in the first quartile was 2·26 (1·52-3·32) for overall mortality, 4·20 (2·03-8·69) for cardiovascular mortality and 1·25 (0·55-2·85) for cancer mortality. These associations remained materially unchanged after multivariate adjustments.


CONCLUSIONS
Low plasma concentrations of homoarginine are a risk marker for overall mortality and especially for cardiovascular mortality in the older general population. Further studies are warranted to elucidate the underlying pathophysiological mechanisms.