Genotype distribution did not deviate from the Hardy– Weinberg equilibrium (P=0.54). R104H, a stabilizing genetic variant previously identified in Asians,18,22 was not detected. Neither risk factors for ischemic vascular disease (Table) nor measures of glucose metabolism, renal function, liver function, or inflammation (Table I in the online-only Data Supplement) differed by T119M genotype, confirming that the effect of genotype on risk of vascular disease was not confounded by risk factors for vascular disease, or other markers of disease, including inflammatory disease. Comparing continuous traits as a function of genotype using parametric t tests did not mark- edly change these results (P values, 0.62–0.86 for Table and 0.05–0.99 for Table I in the online-only Data Supplement).

Whether any of these variants are common in the general population, whether they associate with increased thyroxine and transthyretin levels as markers of increased transthyretin tetramer stabilization, and whether they associate with reduced risk of vascular disease and increased life expectancy in the general population is currently unknown. We tested these hypotheses by genotyping for R104H and T119M in 2 simi- lar studies of the Danish general population, the Copenhagen General Population Study and the Copenhagen City Heart Study, totalling 68 602 participants, of which 10 636 partici- pants developed vascular disease.

TTR T119M Genotype and Plasma Transthyretin

Plasma levels of transthyretin were measured in a total of 1650 participants in the Copenhagen City Heart Study: in all heterozygotes with plasma available (n=35) and in a random sample of noncarriers (n=1615). As previously reported,23 plasma transthyretin levels decreased as a function of age (in 10-year age groups) in both women and men (mean decrease in women and men, respectively, 50 μg/mL and 47 μg/mL; P values for trend <0.0001 from 20 to 80+ years). Mean plasma levels of transthyretin were 16 µg/mL lower in women than in men (Figure I in the online-only Data Supplement; P<0.0001). Results were similar when using parametric tests (P values <0.0001 by linear regression analysis).

Materials and Methods

T119M heterozygotes had a 17% (26 μg/mL) increase in plasma levels of transthyretin compared with noncarriers. Mean transthyretin levels were 183 μg/mL and 157 μg/mL, respectively (Figure 1A; P=0.007). When matching 1:7 by age (in 10-year age groups) and by sex to account for the effect of age and sex on transthyretin levels (Figure I in the online- only Data Supplement), the corresponding increase was 20% (31 μg/mL; Figure 1B; P=0.003). Results were similar

Materials and Methods are available in the online-only Supplement.

Characteristics

Genotyping the Copenhagen City Heart Study and the Copenhagen General Population Study identified 68 281 TTR T119M noncarriers (genotype CC) and 321 TTR T119M

Table. Characteristics of Heterozygotes for TTR T119M (rs28933981) vs Noncarriers in the Copenhagen City Heart Study and the Copenhagen General Population Study Combined

TTR T119M Genotype Noncarriers (CC) Heterozygotes (CT) P Value No. of subjects (%) 68,281 (99.5) 321 (0.47) Age, y 58 (47–67) 56 (47–68) 0.71 Sex (F/M) 37,805/30,476 188/133 0.25 Total cholesterol, mmol/L 5.6 (4.9–6.4) 5.7 (5.0–6.4) 0.88 Triglycerides, mmol/L 1.4 (1.0–2.1) 1.5 (1.0–2.3) 0.41 LDL cholesterol, mmol/L 3.2 (2.6–3.9) 3.2 (2.6–4.0) 0.92 HDL cholesterol, mmol/L 1.6 (1.3–1.9) 1.5 (1.3–1.9) 0.65 Body mass index, kg/m2 26 (23–28) 26 (23–28) 0.63 Hypertension, % 53 55 0.81 Diabetes mellitus, % 4 4 0.60 Smoking, % 61 60 0.69 Physical activity, % 45 45 0.71 Lipid-lowering therapy, % 8 7 0.54

Values are median (interquartile range) or percentage. Diabetes mellitus was self-reported disease, use of insulin, use of oral hypoglycemic drugs, or nonfasting plasma glucose >11 mmol/L. Smoking was active and former smokers. Hypertension was systolic blood pressure≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or use of antihypertensive medication. Physical activity was ≥4 hours per week of light physical activity in leisure time. Lipid-lowering therapy was mainly statins. P values by Mann–Whitney U test or Pearson χ2 test. HDL indicates high-density lipoprotein; and LDL, low-density lipoprotein.

0.003P=0.007P=2© © + a(qw/6r) ujesAujsued |° of}q2°© © + (qu/61) ujesAujsuesCC CT©

Figure 1. Plasma levels of transthyretin in T119M hetero- zygotes vs noncarriers. A, All 1650 participants with trans- thyretin levels measured. B, Heterozygotes matched 1:7 with controls by age (in 10-year age groups) and by sex. Values are mean±standard error of the mean. P values by Mann–Whitney U test. CC indicates noncarriers; and CT, T119M heterozygotes.

0.31 (0.04–2.22; P=0.24) for hemorrhagic stroke (Figure 3). There were no interactions between genotype and study cohort (Copenhagen City Heart Study and Copenhagen General Population Study) on risk of any of the end points mentioned above, indicating a similar effect of genotype on risk in both cohorts (Figure II in the online-only Data Supplement).

after adjusting for age and sex by linear regression analysis (β-coefficient=30, corresponding to a mean increase in trans- thyretin of 30 μg/mL in heterozygotes versus noncarriers; P<0.001, data not shown).

TTR T119M Genotype, Plasma Thyroxine and Other Measures of Thyroid Function

The cumulative incidence of cerebrovascular disease was reduced in T119M heterozygotes versus noncarriers (Figure 4; log rank, P=0.005). At the age of 75 years, the cumulative incidence of cerebrovascular disease was 5% in T119M het- erozygotes and 12% in noncarriers (Figure 4).