The influence of acculturation to a sedentary lifestyle upon the growth and development of lung volumes has been studied in Inuit children aged 9-19 years. Surveys were conducted in the circumpolar community of Igloolik (69 degrees 40'N, 81 degrees W) in 1969/70, 1979/80 and 1989/90. Over this period, the children showed little change of height or body mass at any given age, but a progressive loss of what initially had been a high level of health-related fitness. The sample for each survey comprised about 70% of children in the chosen age range: in the most recent study 87 males and 65 females. Respiratory data included forced vital capacity, one-second forced expiratory volume, maximal mid-expiratory flow rate (second and third surveys only), smoking habits and respiratory health. In each of the 3 surveys, many of the older children in the community were regular smokers. The average cigarette consumption currently rises progressively to 13 +/- 8 cigarettes/day in 87% of males and 11 +/- 7 cigarettes/day in 95% of females over 17 years of age. Nevertheless, lung volumes show the anticipated increase as a logarithmic function of stature. Furthermore, statistically fitted curves show only minor inter-survey differences in volumes for a given standing height. We thus conclude that the deterioration in other aspects of health-related fitness has not yet influenced the growth and development of respiratory function within this Inuit population.
Three surveys (1969/1970, 1979/1980 and 1989/1990) have examined the impact of acculturation to a sedentary lifestyle on the pulmonary function of a circumpolar native Inuit community. The sample comprised more than 50% of those aged 20-60 yrs, most recently 119 males and 92 females. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximal mid-expiratory flow (MMEF) were measured by standard spirometric techniques, and information was obtained on smoking habits and health. Multiple regression equations showed that lung function was affected by height and age, but usually not by age squared. Cross-sectional age coefficients for FVC and FEV1 increased over the period 1969/1970 to 1989/1990. Parallel longitudinal trends were seen in FEV1 (males only). Multiple analysis of variance (MANOVA) showed age-decade*cohort effects for FVC and FEV1 (males but not females). Almost all of the population now smoke (mean +/- SD males 13 +/- 8 cigarettes.day-1; females 11 +/- 7 cigarettes.day-1). However, smoking bears little relationship to lung function perhaps due to limited variance in consumption. About a third of the community have physician-diagnosed and/or radiographically visible chest disease, but with little effect upon pulmonary function. We conclude that an apparent secular trend to a faster ageing of lung function in men is not explained by disease or domestic air pollution. Possible factors include increased lung volumes in young adults, greater pack-years of cigarette exposure, nonspecific respiratory disease, increased inspiration of cold air or altered chest mechanics due to operation of high-speed snowmobiles, and loss of physical fitness.
Secular trends in skinfold thicknesses and body fat distribution were examined in the adult Inuit of Igloolik, N.W.T. through surveys conducted in 1969/70, 1979/80 and 1989/93. Findings were compared with the nGanasan population of Volochanka (Taimir peninsula, Siberia), who were examined in 1992/3. The skinfold readings of the Inuit have increased over the two decades of observation. Currently, the young male Inuit and nGanasan remain relatively thin, but older Inuit men and the women of both populations are now quite obese relative to subjects from Southern Canada. The male Inuit have also developed a centripetal, coronary-prone pattern of fat distribution, with subscapular/triceps skinfold ratios that now exceed averages for southern Canada. The majority of both Inuit and nGanasan are current smokers and many fail to meet minimal standards of aerobic performance. Plasma cholesterol levels are still not very high, but a substantial proportion of the nGanasan are affected by hypertension; their source of animal protein is reindeer meat rather than the marine mammals eaten in Igloolik. Alcohol consumption is also higher in Volochanka than in Igloolik. Action is needed to control smoking, reduce body fat content and increase physical activity if circumpolar populations are not to experience an epidemic of cardiovascular disease.
A 20 year longitudinal study has examined fitness, lung function and exercise electrocardiograms in the Inuit of Igloolik (NWT, 69 degrees 40' N). When first examined (1969/70), an energy expenditure of up to 16 MJ/day was estimated from Kofranyi-Michaelis respirometry. Step test predictions of maximal oxygen intake were also high initially, but values declined progressively with acculturation to a sedentary lifestyle. Throughout the 20 years, right-branch bundle block (RBBB) has been somewhat more prevalent than in southern Canada. The majority of those affected have shown no more than slight R-wave notching. In 1969/70, a few of the more marked cases of RBBB may have been attributable to chronic respiratory disease, but the majority of cases have shown high normal values for both lung function and maximal oxygen intake. We thus conclude that the major cause of RBBB in this community is a ventricular hypertrophy due to the vigorous physical demands of the traditional lifestyle.
The CYP2C19-associated oxidation polymorphism of mephenytoin was investigated in an Inuit population living in the high Arctic of Canada. Results were obtained for 152 subjects, of whom 90 were unrelated to first degree relatives. Phenotyping was based on the capillary gas chromatographic determination of the S/R enantiomeric ratio in overnight urine collected after a dose of 100 mg (R,S)-mephenytoin. The phenotype was confirmed by determining the S/R enantiomeric ratio after acid treatment of urine samples, and for some subjects, by determining urinary recovery of 4'-hydroxymephenytoin using capillary electrophoresis analysis. DNA was analysed for the m1 and m2 mutations of CYP2C19. Three of 152 subjects (2.0%; 95% confidence limits: 0.0-4.2%) were phenotypically classified as poor metabolizers (PMs). Genotype analysis characterized three individuals as homozygous, and 28 individuals as heterozygous for the m1 mutation, the remaining individuals being homozygous for the wild-type allele. The genotype of the three PMs was concordant with that of the phenotype. DNA fingerprinting confirmed that these three individuals were genetically unrelated. The allele frequency of the CYP2C19m1 mutation, determined in unrelated subjects, was 0.12 (95% confidence limits: 0.07-0.17). CYP2C19m2 was not detected in this population. Thus, the Canadian Inuit resemble Caucasian rather than Asian populations in both the incidence of PM phenotype and the molecular basis of the polymorphism.
The xenobiotic oxidation polymorphism associated with cytochrome P450 2D6 (CYP2D6) was investigated in 152 genetically related and unrelated healthy Inuit subjects living in the High Arctic of eastern Canada. Phenotyping was based on HPLC determination of the CYP2D6-related dextromethorphan metabolic ratio in overnight urine samples after oral administration of 30 mg dextromethorphan hydrobromide. The log metabolic ratio was bimodally distributed, with three subjects classified as poor metabolizers (PMs). In subjects unrelated in the first degree, the incidence of the PM phenotype was 3 of 90 or 3.3%. PCR-based analyses of DNA for variants of the CYP2D6 gene demonstrated that the PMs of dextromethorphan had the defective allele CYP2D6*4. The estimated frequency of the CYP2D6*4 allele was 0.067-0.083, which is lower than the frequency in Caucasians but higher than the frequency in Oriental populations. The CYP2D6*3 and the CYP2D6*6 alleles were not detected in the Inuit population. The CYP2D6*10 allele was present in only four unrelated subjects, classified as extensive metabolizers (EMs), resulting in an estimated allele frequency of 0.022, which is much lower than in Oriental populations. This study demonstrated the existence of the CYP2D6 polymorphism in Canadian Inuit, while the frequencies of allelic variants of CYP2D6 point to the uniqueness of this population. Several important therapeutic drugs that are being prescribed in Arctic communities will have altered pharmacokinetics in PMs of CYP2D6.
A longitudinal study has examined the growth of height, sitting height, body mass and triceps skinfolds in a sample of Inuit (281 boys and 266 girls) attending the Igloolik school between the years 1981 and 1989. Heights were around the 10th percentile of U.S. norms for 1970. A peak height velocity of 9.2 +/- 2.3 cm/year was reached by girls at 11.3 +/- 0.7 years, and in boys the peak rate of 8.6 +/- 3.7 cm/year was seen at 13.5 +/- 0.8 years. Sitting heights were also low relative to urban norms. Body mass approached the 50th percentile of U.S. norms, giving a large mass for height ratio at all ages. Triceps thicknesses for the girls were around the 10th percentile of urban norms, and in the boys began around the 25th percentile, but dropped steadily to the 5-10th percentile. No significant differences of growth patterns were seen between cohorts formed from students born in the years 1970/72, 1973/74 and 1975/76. However, comparison with earlier cross-sectional surveys in the same community showed a secular trend to greater stature and greater skinfold readings as the community had become acculturated to such features of modern living as mechanized transport and television. There were no systematic differences of growth rates between the summer and the winter seasons, and nutrition was good throughout. We thus conclude that the short stature has an inherited basis. Attention is drawn to the problem of interpreting curves of growth and weight for height in populations with an unusual body build.
Lipids metabolism and blood lipid profiles in native populations of Northern Asia (Nganasans, n = 43) and Northern Canada (Inuits, n = 151) have been studied. Estimation of serum PUFA of omega-6 and omega-3 series in Nganasans testifies to shifting of their diet to "western" type. Three types of dietary patterns have been observed in inuits: traditional one (among age group of 40-69), "western" (among age group of 18-29) and intermediate, transitional (among age group of 30-39). Age differences in concentrations of total cholesterol, summarized fraction of low density and very low density lipoproteins in Nganasans and Inuits were similar, however, Inuits had higher levels of blood lipids including HDL-cholesterol. Concentrations of apoB lipoproteins were significantly higher in Inuits, however, apoA-1/apoB ratios were estimated as more than 1.0 in both groups and the differences were not significant. Correlation between fatty acid composition and lipid profiles in Inuits who followed traditional diet testify to non-atherogenic type of nutrition. Despite to favorable blood lipid profiles in Northern native population, hypercholesterolemia was found in 2% of Nganasans and 10% of Inuits, while hypo-alpha-cholesterolemia was found in 25% Nganasans and in 5% of Inuits. Thus, changes in dietary patterns of native populations of the Far North have a great influence on blood concentrations of PUFAs of omega-3 series. Changes in the dietary fatty acid composition are considered to be one of the possible reasons of dislipoproteinemia.