Physical Activity and the Risk of Primary Hyperparathyroidism.

ABSTRACT

CONTEXT Primary hyperparathyroidism (P-HPTH) is relatively common and predominantly affects women. Prior studies have shown that physical activity (PA) can lower PTH levels. OBJECTIVE: Our objective was to evaluate the hypothesis that lower PA is a risk factor for developing P-HPTH. DESIGN, SETTING, AND PARTICIPANTS: This prospective cohort study included 69 621 female participants in the Nurses' Health Study I followed for 22 years. EXPOSURES PA and other dietary and demographic exposures were quantified via detailed, and validated, biennial questionnaires. OUTCOMES: Incident P-HPTH was confirmed by medical record review after initial assessment by questionnaire. Adjusted Cox proportional hazards models were used to evaluate whether PA was an independent risk factor for developing P-HPTH. We also evaluated the risk of developing P-HPTH when combining low PA (<16 metabolic equivalent hours/week) with a previously identified independent risk factor for developing P-HPTH low calcium intake (<800 mg/day). The relation between PA and PTH levels was evaluated in 625 participants. RESULTS: We confirmed 302 incident cases of P-HPTH during 1 474 993 person-years of follow-up. Participants in the highest quintile (Q) of PA had a 50% lower risk of developing P-HPTH age-adjusted relative risks and 95% confidence intervals for incident P-HPTH by lowest to highest of PA were Q1 = 1.0 (reference); Q2 = 0.83 (0.60­1.15); Q3 = 0.84 (0.61­1.15); Q4 = 0.50 (0.34­0.74); Q5 = 0.50 (0.35­0.73); P for trend <.001. Extensive multivariable adjustments did not materially change these findings. The adjusted relative risk for developing P-HPTH among participants with the combination lower PA and lower calcium intake was 2.37-fold (1.60­3.51) higher than in participants with higher PA and higher calcium intake. PA was inversely correlated with serum PTH (ρ = −0.09, P = .03); the mean adjusted serum PTH in Q 2­5 of PA was lower than in Q 1 (36.3 vs 39.1 pg/mL, P = .02). CONCLUSION: Low physical activity may be a modifiable risk factor for developing P-HPTH in women.