All-cause, premature, and cardiovascular death attributable to socioeconomic and ethnic disparities among New Zealanders with type 1 diabetes 1994-2019: a multi-linked population-based cohort study

BACKGROUND

New Zealand (NZ) research into type 1 diabetes mellitus (T1DM) mortality can inform policy and future research. In this study we aimed to quantify the magnitude to which ethnicity and socioeconomic disparities influenced mortality at the population level among people with Type 1 diabetes (T1DM) in Auckland, New Zealand (NZ).

METHODS

The cohort data were derived from the primary care diabetes audit program the Diabetes Care Support Service (DCSS), and linked with national primary care, pharmaceutical claims, hospitalisation, and death registration databases. People with T1DM enrolled in DCSS between 1994-2018 were included. All-cause, premature, and cardiovascular mortalities were estimated by Poisson regression models with adjustment for population-level confounders. The mortality rates ratio (MRR) was standardized against the DCSS type 2 diabetes population. Mortality rates were compared by ethnic group (NZ European (NZE) and non-NZE) and socioeconomic deprivation quintile. The population attributable fraction (PAF) was estimated for ethnic and socioeconomic disparities by Cox regression adjusting for demographic, lifestyle, and clinical covariates. The adjusted slope index inequality (SII) and relative index of inequality (RII) were used to measure the socioeconomic disparity in mortalities.

RESULTS

Overall, 2395 people with T1DM (median age 34.6 years; 45% female; 69% NZE) were enrolled, among whom the all-cause, premature and CVD mortalities were 6.69 (95% confidence interval: 5.93-7.53), 3.30 (2.77-3.90) and 1.77 (1.39-2.23) per 1,000 person-years over 25 years. The overall MRR was 0.39 (0.34-0.45), 0.65 (0.52-0.80), and 0.31 (0.24-0.41) for all-cause, premature and CVD mortality, respectively. PAF attributable to ethnicity disparity was not significantly different for mortality. The adjusted PAF indicated that 25.74 (0.84-44.39)% of all-cause mortality, 25.88 (0.69-44.69)% of premature mortality, 55.89 (1.20-80.31)% of CVD mortality could be attributed to socioeconomic inequality. The SII was 8.04 (6.30-9.78), 4.81 (3.60-6.02), 2.70 (1.82-3.59) per 1,000 person-years and RII was 2.20 (1.94-2.46), 2.46 (2.09-2.82), and 2.53 (2.03-3.03) for all-cause, premature and CVD mortality, respectively.

CONCLUSIONS

Our results suggest that socioeconomic disparities were responsible for a substantial proportion of all-cause, premature and CVD mortality in people with T1DM in Auckland, NZ. Reducing socioeconomic barriers to management and self-management would likely improve clinical outcomes.

Effect of onset of type 2 diabetes on risks of cardiovascular disease and heart failure among new Zealanders with impaired glucose tolerance over 25 years: tapered-matched landmark analysis

BACKGROUND

This study aimed to examine the association between the incident onset of T2DM and 5- and 10-year risks of CVD and HF in people with IGT identified in primary care in South and West Auckland, New Zealand (NZ) between 1994 and 2019.

METHODS

We compared CVD and HF risks in patients with IGT and with/without T2D newly diagnosed within the exposure window (1-5 years). Tapered matching and landmark analysis (to account for immortal bias) were used to control for potential effects of known confounders.

RESULTS

Among 26,794 patients enrolled with IGT, 845 had T2D newly diagnosed within 5 years from enrolment (landmark date) and 15,452 did not have T2D diagnosed. Patients progressing to T2D (vs. those not progressing) had a similar 5-year risk for CVD (hazard ratio 1.19; 95% CI 0.61-2.32) but significantly higher 10-year risk of CVD (2.45(1.40-4.29)), 5-year risk of HF (1.94(1.20-3.12)) and 10-year risk of HF (2.84(1.83-4.39). The association between the onset of T2D and risk of 10-year risk of CVD, 5-year and 10-year risk of HF was more likely among men, the socioeconomically deprived, those currently smoking, patients with higher metabolic measures and/or those with lower renal function. Patients of NZ European ethnicity had a lower 10-year risk of CVD.

CONCLUSIONS

The study suggests that the diagnosis of T2D mediates the risk of CVD and HF in people with IGT. The development of risk scores to identify and better manage individuals with IGT at high risk of T2D is warranted.

Adverse Clinical Outcomes Attributable to Socioeconomic and Ethnic Disparities Among People with Type 2 Diabetes in New Zealand Between 1994-2018: A Multiple Linked Cohort Study

Purpose

The study aimed to examine the separate population-level contributions of the ethnic and socioeconomic disparities among people with type 2 diabetes mellitus (T2DM) and residence in New Zealand (NZ).

Patients and Methods

A prospective cohort enrolled T2DM patients from 01/01/1994 into the Diabetes Care Support Service, a primary care audit program in Auckland, NZ. The cohort was linked to national registry databases (socioeconomic status, pharmaceutical claim, hospitalization, and death registration). Each cohort member was followed up till death or the study end time (31/12/2019), whichever came first. Incident clinical events (stroke, myocardial infarction (MI), heart failure (HF), end-stage renal disease (ESRD), and premature mortality (PM)) were used as outcomes. The attributable fractions (AFs) were estimated for the whole population and for specific population with NZ Europeans (NZE) and/or least deprived population as reference, both unadjusted and with adjustment for covariables by Cox Regression models.

Results

Among 36,267 patients, adjusted population AFs indicated 6.6(-30.8-33.3)% of PM, 17.1(5.8-27.0)% of MI, 35.3(22.6-46.0)% of stroke, 14.3(3.2-24.2)% of HF, and 15.9(6.7-24.2)% of ESRD could be attributed to deprivation; while 14.3(3.3-25.4)% of PM, -3.3(-8.3-1.5)% of MI, -0.5(-6.7-5.3)% of stroke, 4.7(0.3-8.8)% of HF, 13.3(9.9-16.6)% of ESRD could be attributed to ethnicity. Deprivation contributed a significant AF to stroke, while ethnicity was important for ESRD. Gradient of AF for deprivation indicated NZE and Asians were most affected by deprivation across outcomes. Conversely, Māori, with the highest AFs for ethnicity of PM and ESRD, were unaffected by deprivation. At same deprivations, the AFs of MI and stroke were greatest among NZE compared with other ethnic groups; the AF of ESRD was greatest among Māori and Pasifika.

Conclusion

Both socioeconomic deprivation and ethnicity are strongly associated with outcomes in patients with T2DM in NZ, although the extent of the deprivation gradient is greatest among NZE and Asians, and least among Māori.

Ethnic differences in 25-year risk of incident chronic kidney disease among people with type 2 diabetes in New Zealand

INTRODUCTION

Insights into ethnic differences in the natural history of chronic kidney disease (CKD) among people with type 2 diabetes mellitus (T2DM) might inform clinical strategies to address disparities in hospitalization and mortality. Risks of CKD II-V stages over a 25-year period between New Zealand Europeans (NZEs), Māori and Pasifika, and with T2DM in Auckland, New Zealand (NZ) were compared.

RESEARCH DESIGN AND METHODS

As a primary care audit program in Auckland, the Diabetes Care Support Service was linked with national registration databases. People with existing CKD II-V were ruled out. To balance potential confounders, we applied a tapered matching method . 'Quasi-trial'-matched cohorts were set up separately between Māori and NZE and between Pasifika and NZE. Ethnic population differences in risk of any and each stage of CKD over 1994-2018 were examined by weighted Cox regression model.

RESULTS

The HRs for developing any CKD, CKD stages II-V for Māori (n=2215) versus NZE (n=2028) were 1.18 (95% CI 0.99 to 1.41), 1.10 (95% CI 0.91 to 1.32), 1.70 (95% CI 1.19 to 2.43), 3.93 (95% CI 2.16 to 7.14), and 3.74 (95% CI 1.74 to 8.05), respectively. Compared with NZE (n=2474), the HRs for developing any CKD, CKD stages II-V for Pasifika (n=3101) were 1.31 (95% CI 1.09 to 1.57), 1.26 (95% CI 1.05 to 1.52), 1.71 (95% CI 1.14 to 2.57), 3.75 (95% CI 1.40 to 10.05), and 4.96 (95% CI 1.56 to 15.75), respectively.

CONCLUSIONS

Among people with T2DM in NZ, significant ethnic differences exist in the risk of progressing to each stage of CKD (stage V in particular). Mechanism studies underlying these differences, as well as the need for identification of biomarkers to predict the early onset renal lesion, are warranted.

Ethnic differences in metabolic achievement between Māori, Pacific, and European New Zealanders with type 2 diabetes

AIMS

To compare variations in metabolic target achievement by ethnicity (Europeans, Māori and Pasifika) among patients with type 2 diabetes (T2DM) in Auckland, New Zealand (NZ) between 1994 and 2013.

METHODS

32,237 patients were enrolled. Adjusted marginal difference (European as reference) of systolic blood pressure (SBP), body mass index (BMI), HbA1c and total cholesterol, alongside the proportion achieving metabolic targets were estimated using multivariable mixed effect models at baseline, 1-, 2-, 3-, 4-, and 5-years, adjusted for covariates.

RESULTS

Compared with Europeans, Māori and Pasifika had continuously, significantly higher HbA1c (by 0.3% (+3.5 mmol/mol) and 0.6% (+6.8 mmol/mol) respectively and BMI (+1.5 and +0.3 kg/m² respectively) but lower SBP (-1.8 and -3.4 mmHg respectively) and TG (-0.03 and -0.34 mmol/L respectively), and insignificantly TC (+0.004 and +0.01 respectively), by 5-years of follow-up. While 49% Europeans were within target HbA1c, this was achieved by only 30% Māori and 27% Pasifika. Conversely, 41% Europeans, 46% Māori and 59% Pasifika achieved the SBP target (all P < 0.0001).

CONCLUSIONS

Managing hyperglycemia appears to be more challenging than treating hypertension and dyslipidemia among Māori and Pasifika. New anti-hyperglycemia treatments, addressing health literacy, socioeconomic and any cultural barriers to management and self-management are urgently needed to reduce these disparities.

Ethnic Differences in Cancer Rates Among Adults With Type 2 Diabetes in New Zealand From 1994 to 2018

IMPORTANCE

People with type 2 diabetes have greater risk for some site-specific cancers, and risks of cancers differ among racial and ethnic groups in the general population of Aotearoa New Zealand. The extent of ethnic disparities in cancer risks among people with type 2 diabetes in New Zealand is unclear.

OBJECTIVE

To compare the risks of 21 common adult cancers among Māori, Pasifika, and New Zealand European individuals with type 2 diabetes in New Zealand from 1994 to 2018.

DESIGN, SETTING, AND PARTICIPANTS

This population-based, matched cohort study used data from the primary care audit program in Auckland, New Zealand, linked with national cancer, death, and hospitalization registration databases, collected from January 1, 1994, to July 31, 2018, with follow-up data obtained through December 31, 2019. Using a tapered matching method to balance potential confounders (sociodemographic characteristics, lifestyle, anthropometric and clinical measurements, treatments [antidiabetes, antihypertensive, lipid-lowering, and anticoagulant], period effects, and recorded duration of diabetes), comparative cohorts were formed between New Zealand European and Māori and New Zealand European and Pasifika individuals aged 18 years or older with type 2 diabetes. Sex-specific matched cohorts were formed for sex-specific cancers.

EXPOSURES

Māori, Pasifika, and New Zealand European (reference group) ethnicity.

MAIN OUTCOMES AND MEASURES

The incidence rates of 21 common cancers recorded in nationally linked databases between 1994 and 2018 were the main outcomes. Weighted Cox proportional hazards regression was used to assess ethnic differences in risk of each cancer.

RESULTS

A total of 33 524 adults were included: 15 469 New Zealand European (mean [SD] age, 61.6 [13.2] years; 8522 [55.1%] male), 6656 Māori (mean [SD] age, 51.2 [12.4] years; 3345 [50.3%] female), and 11 399 Pasifika (mean [SD] age, 52.8 [12.7] years; 5994 [52.6%] female) individuals. In the matched New Zealand European and Māori cohort (New Zealand European: 8361 individuals; mean [SD] age, 58.9 [12.9] years; 4595 [55.0%] male; Māori: 5039 individuals; mean [SD] age, 51.4 [12.3] years; 2542 [50.5%] male), significant differences between New Zealand European and Māori individuals were identified in the risk for 7 cancers. Compared with New Zealand European individuals, the hazard ratios (HRs) among Māori individuals were 15.36 (95% CI, 4.50-52.34) for thyroid cancer, 7.94 (95% CI, 1.57-40.24) for gallbladder cancer, 4.81 (95% CI, 1.08-21.42) for cervical cancer (females only), 1.97 (95% CI, 1.30-2.99) for lung cancer, 1.81 (95% CI, 1.08-3.03) for liver cancer, 0.56 (95% CI, 0.35-0.90) for colon cancer, and 0.11 (95% CI, 0.04-0.27) for malignant melanoma. In the matched New Zealand European and Pasifika cohort (New Zealand European: 9340 individuals; mean [SD] age, 60.6 [13.1] years; 4885 [52.3%] male; Pasifika: 8828 individuals; mean [SD] age, 53.1 [12.6] years; 4612 [52.2%] female), significant differences between New Zealand European and Pasifika individuals were identified for 6 cancers. Compared with New Zealand European individuals, HRs among Pasifika individuals were 25.10 (95% CI, 3.14-200.63) for gallbladder cancer, 4.47 (95% CI, 1.25-16.03) for thyroid cancer, 0.48 (95% CI, 0.30-0.78) for colon cancer, 0.21 (95% CI, 0.09-0.48) for rectal cancer, 0.21 (95% CI, 0.07-0.65) for malignant melanoma, and 0.01 (95% CI, 0.01-0.10) for bladder cancer.

CONCLUSIONS AND RELEVANCE

In this cohort study, differences in the risk of 21 common cancers were found between New Zealand European, Māori, and Pasifika groups of adults with type 2 diabetes in New Zealand from 1994 to 2018. Research into the mechanisms underlying these differences as well as additional screening strategies (eg, for thyroid and gallbladder cancers) appear to be warranted.

Prospective 10-year study of postmenopausal women with asymptomatic primary hyperparathyroidism

AIM

There are few prospective studies of people with asymptomatic primary hyperparathyroidism (PHPT) who have not had parathyroidectomy. We followed a group of postmenopausal women with asymptomatic PHPT for up to 10 years to determine whether they could be managed conservatively without parathyroidectomy.

METHODS

A 10-year, prospective, longitudinal study of 23 postmenopausal women with asymptomatic PHPT initially enrolled into a 4-year randomised controlled trial of hormone replacement therapy. Serum total and ionised calcium, biochemistry, urine calcium, and bone mineral density were measured every 6-12 months.

RESULTS

Serum ionised calcium, creatinine, and urine calcium:creatinine remained stable throughout follow-up. In contrast, there was a steady increase in the total and adjusted serum calcium and a small rise in serum PTH. Only one woman had an adjusted serum calcium >3.0 mmol/L during follow-up. There were few other clinical events possibly related to PHPT (1 possible episode of nephrolithiasis, 4 fractures, 1 severe osteoporosis). Three women underwent parathyroidectomy, although 19/23 women met the updated criteria for parathyroidectomy from the 2002 NIH-sponsored workshop during follow-up.

CONCLUSIONS

Many postmenopausal women with asymptomatic PHPT do not develop symptoms or complications of PHPT, and their biochemical parameters remains stable. Therefore, such asymptomatic women with PHPT can often be managed conservatively without parathyroidectomy.

Addition of monofluorophosphate to estrogen therapy in postmenopausal osteoporosis: a randomized controlled trial

INTRODUCTION

Treatment of osteoporosis with high-dose fluoride alone does not reduce fracture risk. We hypothesized that the antifracture efficacy of fluoride could be optimized by its use in low doses combined with an antiresorptive agent.

EXPERIMENTAL SUBJECTS

Subjects included 80 women with postmenopausal osteoporosis who had been taking estrogen for at least 1 yr.

METHODS

Subjects were randomized to receive monofluorophosphate (MFP) (fluoride content of 20 mg/d) or placebo over 4 yr in a double-blind trial.

RESULTS AND DISCUSSION

There were progressive increases in lumbar spine bone density over the duration of the study (MFP, 22%; placebo, 6%; P < 0.0001). In the trabecular bone of L3, these increases were even greater (MFP, 49%; placebo, 2.5%; P < 0.0001). In the proximal femur, there were smaller but significant treatment effects (P = 0.015). Total body scans and their subregions also showed significantly greater increases in the MFP group. Bone formation markers increased significantly in the MFP group at yr 1. Hyperosteoidosis was present in biopsies from five of seven MFP subjects, with osteomalacia in two of seven. The hazards ratio for vertebral fractures was 0.20 (95% confidence interval, 0.05-1.30), and the incidence rate ratio was 0.12 (95% confidence interval, 0.06-0.23; P < 0.01). The hazards ratio for nonvertebral fractures was 3.3 (95% confidence interval, 0.8-12.0).

CONCLUSIONS

We conclude that fluoride at 20 mg/d produces substantial increases in bone mineral density but still interferes with bone mineralization. This indicates that most previous studies with this ion have used toxic doses and that much lower doses should be assessed to find a safe dose window for the use of this powerful anabolic agent.

Thyrotoxic, hypokalaemic periodic paralysis: Polynesians, an ethnic group at risk

BACKGROUND

Thyrotoxic, hypokalaemic periodic paralysis (TPP) is a reversible cause of severe muscle weakness that occurs in a small minority of thyrotoxic patients. Most cases to date have been reported in Asian men.

AIMS

To evaluate the ethnic distribution of patients with TPP.

METHODS

Retrospective analysis of all patients presenting with thyrotoxicosis and hypokalaemia with paralysis to two New Zealand hospitals.

RESULTS

Seventy-one per cent of the 21 patients with TPP were of Polynesian ethnicity (Maori and Pacific Islander), 24% Asian and 5% European. Based on population demographics, these figures suggest a 37-fold overrepresentation for Polynesians and 159-fold for Asians compared with New Zealand Europeans.

CONCLUSION

Polynesian, in addition to Asian people, are two ethnic groups at particular risk of TPP, and this condition must be considered in the differential diagnosis for patients presenting to the emergency department with severe hypokalaemia and weakness.

The effect of treatment with a thiazide diuretic for 4 years on bone density in normal postmenopausal women

SUMMARY

We performed a 2-year extension of our previous 2-year randomized controlled trial of the effects of hydrochlorothiazide on bone mineral density. The improvements in bone density seen in the first 2 years were sustained throughout the extension study. Thiazides provide a further option in the prevention of postmenopausal bone loss.

INTRODUCTION

Thiazide diuretics reduce urinary calcium excretion and therefore might prevent osteoporosis. Previously we reported a 2-year randomized controlled trial of hydrochlorothiazide treatment in 185 postmenopausal women that showed positive benefits of hydrochlorothiazide on bone density. Here, we report the results of a 2-year extension to that study.

METHODS

Of 185 healthy postmenopausal women, 122 agreed to continue in a double-blinded 2-year extension taking 50 mg hydrochlorothiazide or placebo daily. Measurements of bone density occurred every 6 months and of calcium metabolism at 2 and 4 years.

RESULTS

The improvements in bone density seen in the first 2 years of the trial were sustained throughout the extension. There were significant between-groups differences in the change in bone density over 4 years at the total body (0.9%, P<0.001), legs (1.0%, P=0.002), mid-forearm (1.1%, P=0.03), and ultradistal forearm (1.4%, P=0.04). At the lumbar spine (0.9%, P=0.76) and femoral neck (0.4%, P=0.53) the between-groups differences did not reach statistical significance.

CONCLUSIONS

Hydrochlorothiazide produces small positive benefits on cortical bone density that are sustained for at least the first 4 years of treatment. They provide a further option in the prevention of postmenopausal bone loss, especially for women with hypertension or a history of kidney stones.

Hydrochlorothiazide reduces loss of cortical bone in normal postmenopausal women: a randomized controlled trial

PURPOSE

Thiazide diuretics reduce urine calcium excretion and might therefore reduce postmenopausal bone loss. In some, but not all, case-control studies, their use has been associated with a reduced incidence of hip fractures. We studied the effects of hydrochlorothiazide on bone loss in normal postmenopausal women.

SUBJECTS AND METHODS

We performed a randomized, double-blind, 2-year trial of the effects of hydrochlorothiazide (50 mg per day) and placebo on bone mineral density in normal postmenopausal women. Participants were not required to have either low bone mineral density or hypertension. Bone mineral density was measured using dual-energy x-ray absorptiometry.

RESULTS

One hundred eighty-five women entered the study, of whom 138 completed 2 years of follow-up. In an intention-to-treat analysis, hydrochlorothiazide produced significant benefits on bone mineral density of the total body (between-group difference at 2 years of 0.8%, 95% confidence interval [CI]: 0.3% to 1.3%, P <0.0001), legs (0.9%, 95% CI: 0.2% to 1.7%, P <0.0001), mid-forearm (1.2%, 95% CI: 0.2% to 2.2%, P = 0.02), and ultradistal forearm (1.7%, 95% CI: 0.1% to 3.2%, P = 0.04). There was no effect in the lumbar spine (0.5%, 95% CI: -0.5% to 1.6%) or femoral neck (0.2%, 95% CI: 1.3% to 1.7%). The between-group changes tended to be greatest during the first 6 months, except in the mid-forearm where there appeared to be a progressive divergence. An as-treated analysis produced similar results. Urine calcium excretion and indices of bone turnover decreased in the thiazide group, but parathyroid hormone concentrations did not differ between the groups. Treatment was tolerated well.

CONCLUSIONS

Hydrochlorothiazide (50 mg per day) slows cortical bone loss in normal postmenopausal women. It may act directly on bone as well as on the renal tubule. The small size of the effect suggests that thiazides may have a role in the prevention of postmenopausal bone loss, but that they are not an appropriate monotherapy for treating osteoporosis.

Effects of hormone replacement therapy on bone mineral density in postmenopausal women with primary hyperparathyroidism: four-year follow-up and comparison with healthy postmenopausal women

BACKGROUND

Long-term treatment of patients with asymptomatic primary hyperparathyroidism remains controversial, but the presence of osteoporosis is regarded as an indication for parathyroidectomy. Hormone replacement therapy (HRT) is a possible alternative therapy in osteopenic postmenopausal women with the disorder, and results of short-term studies suggest a beneficial effect on bone mass comparable to that achieved by parathyroidectomy. Longer-term data are required to further assess the efficacy of this treatment in chronic stable primary hyperparathyroidism.

METHODS

We report the results of the extension from 2 to 4 years of a randomized, placebo-controlled trial of HRT in postmenopausal women with primary hyperparathyroidism. Of 23 postmenopausal women with primary hyperparathyroidism, 11 received active HRT with conjugated equine estrogen, 0.625 mg/d, and medroxyprogesterone acetate, 5 mg/d, and 12 received placebo. Bone mineral density was measured throughout the skeleton at 6-month intervals using dual-energy x-ray absorptiometry in these women and in 50 normocalcemic age-matched control subjects. None of the 23 patients withdrew during the extension period.

RESULTS

Changes in bone mineral density were more positive in those taking HRT than placebo, with the between-group differences at 4 years being 4.6% in the total body, 7.5% in the lumbar spine, 7.4% in the femoral neck, 8.2% in the femoral trochanter, 6.8% in the legs, and 7.0% in the forearm (P<.01). At skeletal sites composed predominantly of cortical bone, there was a progressive divergence of the 2 groups. Biochemical markers of bone turnover remained lower throughout the study in women taking HRT. When rates of bone loss were compared between the placebo group and healthy women of comparable age, bone loss tended to be more marked throughout the skeleton in women with hyperparathyroidism, but only in the total body and its legs subregion was this difference significant.

CONCLUSIONS

Hormone replacement therapy is efficacious in the long-term management of osteopenia in postmenopausal women with primary hyperparathyroidism and thus represents an important new therapeutic option for asymptomatic patients who do not have other indications for surgery. Bone loss seems to be accelerated in untreated primary hyperparathyroidism.

Hormone replacement therapy causes a respiratory alkalosis in normal postmenopausal women

Menopause is associated with an increase in venous bicarbonate concentrations that is reversible with hormone replacement therapy (HRT). However, the mechanism underlying this effect is not known. To address this question, we studied the changes in acid-base indexes in the arterialized venous blood of normal postmenopausal women commencing conjugated equine estrogen (0.625 mg/day), medroxyprogesterone acetate (MPA; 5 mg/day), their combination, or placebo, in a double blind randomized controlled study over 3 months. Serum bicarbonate concentrations decreased significantly in the groups receiving either MPA or estrogen plus MPA (P = 0.008). This trend was apparent as early as 2 days and reached 2.7 and 2.3 mmol/L in the respective groups by 3 months. Similar changes were seen with partial pressure of carbon dioxide (P = 0.04); a change of -0.7 kPa occurred in the estrogen plus MPA group at 3 months. There were no changes in bicarbonate concentrations or partial pressure of carbon dioxide in those receiving estrogen alone or placebo. Accompanying changes in blood pH were apparent in the estrogen plus MPA group, where there was an upward trend at 1 week (P = 0.056) and a significant change from baseline (+0.013) at 3 months (P = 0.03). In the whole group, the changes in pH were inversely correlated with those in urinary excretion of hydroxyproline (r = -0.44; P = 0.01). We conclude that HRT using conjugated estrogens and MPA produces small, but sustained, changes in acid-base status. These may contribute to the effects of HRT and menopause on many tissues and disease processes, including the development of osteoporosis.

The effect of past use of the injectable contraceptive depot medroxyprogesterone acetate on bone mineral density in normal post-menopausal women

OBJECTIVE

Depot medroxyprogesterone acetate (DMPA), an injectable progestogen, is a widely used contraceptive acting primarily by inhibiting secretion of pituitary gonadotrophins, thus producing oestrogen deficiency. Cross-sectional and prospective studies in pre-menopausal women have shown DMPA use to be associated with reduced bone density, but bone density increases following discontinuation of the drug. Because fracture rates are low in pre-menopausal women, the principal concern arising from the effects of DMPA on bone is that there may be residual osteopenia in former users such that their post-menopausal fracture risk is increased. The present study addresses this question.

DESIGN

Cross-sectional study of bone density in post-menopausal former users of DPMA and controls.

SUBJECTS

Three hundred and forty-six normal post-menopausal women, of whom 34 had previously used DMPA. The median age at which DMPA use began was 41 years and the median duration of use was 3.0 years.

MEASUREMENTS

Bone density was measured in the spine, proximal femur and total body by dual-energy, X-ray absorptiometry.

RESULTS

There were no significant differences in bone density at any site between the women who had previously used DMPA and the others in the cohort. However, in those who had used DMPA for > 2 years there was a trend towards bone densities being lower in the former users, the differences from non-users being 1.6% in the lumbar spine (P = 0.6), 3.1% in the femoral neck (P = 0.4) and 0.5% in the total body (P = 0.8). There was no correlation between bone densities and the duration of DMPA use, the age at discontinuation of DMPA, or the time between DMPA discontinuation and the menopause.

CONCLUSIONS

Any residual effects of depot medroxyprogesterone acetate use on post-menopausal bone density are small and therefore unlikely to have a substantial impact on fracture risk in the post-menopausal years.

Premature hair graying and bone mineral density

In a recent case-control study, premature hair graying was found to be associated with osteopenia, suggesting that this might be a clinically useful risk factor for osteoporosis. We report a reexamination of this possibility in 293 healthy postmenopausal women. Subjects experiencing onset of hair graying in their 20s tended to have lower bone mineral density throughout the skeleton (adjusted for age and weight) than those with onset of graying later in life. The same was true for those in whom the majority of their hair was gray by the age of 40 yr (n = 16), in whom bone density was reduced by 7% in the femoral neck, 8% in the femoral trochanter, and 4% in the total body (P < 0.05) when compared with those not prematurely gray. Bone density at the lumbar spine and Ward's triangle showed similar trends that were not significant. However, premature hair graying explained only 0.6-1.3% of the variance in bone mineral density within the population. We conclude that premature hair graying is associated with low bone density, but that its infrequency in the normal postmenopausal population leads to its accounting for only a tiny fraction of the variance of bone density.