Fine-scale population structure of Malays in Peninsular Malaysia and Singapore and implications for association studies.

Fine scale population structure of Malays - the major population in Malaysia, has not been well studied. This may have important implications for both evolutionary and medical studies. Here, we investigated the population sub-structure of Malay involving 431 samples collected from all states from peninsular Malaysia and Singapore. We identified two major clusters of individuals corresponding to the north and south peninsular Malaysia. On an even finer scale, the genetic coordinates of the geographical Malay populations are in correlation with the latitudes (R(2) = 0.3925; P = 0.029). This finding is further supported by the pairwise FST of Malay sub-populations, of which the north and south regions showed the highest differentiation (FST [North-south] = 0.0011). The collective findings therefore suggest that population sub-structure of Malays are more heterogenous than previously expected even within a small geographical region, possibly due to factors like different genetic origins, geographical isolation, could result in spurious association as demonstrated in our analysis. We suggest that cautions should be taken during the stage of study design or interpreting the association signals in disease mapping studies which are expected to be conducted in Malay population in the near future.

Impact of different dietary sodium reduction strategies on blood pressure: a systematic review.

High sodium intake was found to be associated with increased blood pressure. Decreasing dietary sodium intake can effectively reduce blood pressure, especially among hypertensive individuals, but the extent of reduction remains debatable. The effectiveness of different sodium reduction strategies on blood pressure reduction was identified in the current review. Randomized controlled trials and clinical trials on dietary sodium intake and blood pressure published from 23 March 2008 to 23 March 2021 were collected from the PubMed database. Twenty-six studies were included and divided into four subgroups based on the types of interventions identified. Subgroups included a low-sodium diet (1) in a group with or without added sodium, (2) through food substitutes, (3) through health education and behavior change, and (4) through salt substitutes. Reduction of dietary sodium intake resulted in a mean difference of 4.51 mmHg (95% CI: 3.35-5.67) in systolic blood pressure and 2.42 mmHg (95% CI: 1.61-3.23) in diastolic blood pressure. The effectiveness of these strategies was approximated from the difference in 24-h urinary sodium excretion between the intervention and control groups, which was 53.74 mmol/day (95% CI: 31.95-75.53). When analyzed, the low-sodium diet without added sodium showed the greatest significant differences in blood pressure (7.58/4.01 mmHg) and 24-h urinary sodium excretion (101.49 mmol/day), whereas the low-sodium diet through food substitutes yielded the lowest significant differences in blood pressure (2.26/0.81 mmHg) and 24-h urinary sodium excretion (25.78 mmol/day). Thus, reducing sodium intake can be an effective strategy for the prevention and treatment of hypertension.